List of Chemical Compounds

A pure chemical substance consisting of two or more different chemical elements which can be separated into simpler substances by chemical reactions is called chemical compound. They exhibit a unique and defined chemical structure. Chemical compounds may be molecular compounds which are held together by covalent bonds, salts by ionic bonds, intermetallic compounds by metallic bonds, or complexes by coordinate covalent bonds. Pure chemical elements are not referred as chemical compounds if they contain molecules which have multiple atoms of a single element like H2, S8.

Introduction:

Elements turn into compounds and become more stable. When compounds have the maximum number of possible electrons in their outermost energy level, which is normally two or eight valence electrons, they become stable. For this reason only noble gases do not react very fast as they have eight valence electrons.

List of Compounds

Compounds are classified into the following three lists:

1) List of inorganic compounds: These compounds are without a C-H bond

2) List of organic compounds: These compounds are with a C-H bond

3) List of biomolecules.

List for Chemical Compounds

Acetic acid

Acetylcholine

Agar

Amylase

Ascorbic acid (vitamin C)

Asparagines

Aspartic acid

Auxin

Bilirubin 

Biotin (Vitamin H)

Caffeine

Calciferol (Vitamin D)

calcitonin

Cannabinol

Casein

Cellulose

Chlorophyll

Cholecystokinin (CCK)

Cholesterol

Choline

Citric acid

Citrulline

Cobalamin (vitamin B12)

Coenzyme

Colchicine

Collagen

Cysteine

Cystine

Cytidine

Cytochalasin

Deoxyribose

Deoxyribose nucleic acid (DNA)

Dopamine

Enzyme

Ephedrine

Epinephrine – C9H13NO3

Fatty acid

Fibrin

Folic acid (Vitamin M)

Follicle stimulating hormone (FSH)

Formaldehyde

Formic acid

Fructose

Galactose

Gastrin

Gelatin

Globulin

Glucagon 

Glucose – C6H12O6

Glucose oxidase

Glycine

Glycogen

Glycolic acid

Glycoprotein

Gonadotropin-releasing hormone (GnRH)

Growth hormone

GTPase

Guanine

Guanosine

Guanosine triphosphate (+GTP)

Hemocyanin

Hemoglobin

Histamine

Histidine

Histone

Histone methyltransferase

Hormone

Human growth hormone

Inositol

Insulin

Integral membrane protein

Integrase

Interferon

Isoleucine

Keratin

Kinase

Lactase

Lactic acid

Lactose

Leucine

Linoleic acid

Linolenic acid

Lipase

Lipid

Luteinizing hormone (LH)

Lysine

Lysozyme

Malic acid

Maltose

Melatonin

Membrane protein

Metalloprotein

Myoglobin

Myosin

Nucleic Acid

Oestrogens

Ornithine

Oxalic acid

Oxidase

Paclitaxel

Palmitic acid

Pantothenic acid (vitamin B5)

parathyroid hormone (PTH)

Penicillin

Pepsin

Peripheral membrane protein

phosphatase

Phospholipid

Phenylalanine

Polysaccharide

Porphyrin

Progesterone

Prolactin (PRL)

Proline

Propionic acid

Protamine

Protease

Protein

Proteinoid

Pyruvic acid

Quinone

Raffinose

RNA - Ribonucleic acid

RuBisCO

Sucrose (sugar)

Sugars (in general)

Tartaric acid 

Topoisomerase

Tyrosine

Uracil

Urea

Urease

Uric acid – C5H4N4O3

Uridine

Valine

Vasopressin

Vitamins (in general)

Water

Xylose

Check my best blog Oxidaton.

Oxidaton

Oxidation is a process in which Oxygen is added to a element or when hydrogen is removed from the molecule or electrons are removed from the atom.

Introduction:

For example:

2H₂(g)  + O_2(g)  ------> 2H₂O(g)
2Mg(s)  + O_2(g)  -----> 2MgO(s)

Here hydrogen is oxidized because oxygen is added to Hydrogen. Magnesium is also oxidized by oxygen.
2H₂S(g)   + O2(g)    ----> 2S(s)  + 2H2O(l)

In the above reaction H₂S is oxidized since Hydrogen is removed from H₂S
Zn (s)--------> Zn²⁺ (aq) + 2e-

In the above example the Zinc is oxidized into Zn²⁺. Zinc looses two electron to form the ion. Since it looses electron it is oxidation. Oxidation is a part of redox reaction. In this type of reaction reduction and oxidation takes place simultaneously.

Addition of other electronegative elements are also considered as oxidation.For example
Mg(s) +  F₂(g)  -----> MgF₂(s)
2K(s)  + Cl₂(g)  ----> 2KCl(s)

In the above example Magnesium is oxidized to Mg²⁺ by flourine and  potassium is oxidized to K⁺ by the chlorine. 

Examples of Oxidaton Reaction

Combustion of methane is an example of oxidation reaction.  For example methane is oxidized to carbon dioxide and water when ignited
CH₄  +2 O₂  ----->  CO₂  + 2H₂O
Iron article is oxidized to Fe₃O₄ when exposed to air and water. Oxidation is unwanted in the case of iron and to prevent it normally painting is done on the Iron.  Galvanization of Iron is another method to prevent the oxidation of Iron which is called as corrosion.   Chrome plating of Iron is another method in which Iron is coated with Chromium so that the iron is not oxidized.
Oxidation process finds many application.  Redox reaction which involves oxidation and reduction is used for volumetric determination of unknown amount of substance from the known amount of the compound.

Molecular Orbital Energy

Introduction

A molecular orbital energy level diagram is a qualitative descriptive tool explaining chemical bonding in molecules in terms of molecular orbital theory in general and the Linear combination of atomic orbitals molecular orbital method in particular.

Molecular Orbital Energy

Molecular orbital energy depends upon the two factors:

(i) The energies of the atomic orbitals gets combine to form molecular orbitals.

(ii) The overlapping between the atomic orbitals.

Greater the overlapping, more the bonding orbital is lowered and the antibonding orbital is raised in energy relative to atomic orbitals. For e.g; the extent of overlapping in case of s - orbital is greater than that in p - orbital. Consequently, the energy of a s2p_z is lesser than the energy of bonding p2p_x or p2p_y MOs.

Now, 1s atomic orbitals of two atoms form two molecular orbitals named as s1s and s*1s. The 2s and 2p orbitals form four bonding molecular orbitals and four antibonding molecular orbitals as:

Bonding molecular orbitals:

s2s, s2p_z , p2p_x , p2p_y

Antibonding molecular orbitals:

s*2s, s *2p_z, p*2p_x, p*2p_y

The energy levels of these molecular orbitals have been examined experimentally by spectroscopic methods. The order of increasing molecular orbital’s energy is obtained by the combination of 1s, 2s and 2p orbitals of two atoms is:

s1s, s*1s, s2s, s*2s, s2p_z, p2P_x = p2p_y, p*2p_x = p*2p_y, s*2p_z

Here the energy of molecular orbitals increases from s1s to s*2p_z.

However, experimental proofs for some diatomic molecules have shown that above sequence of energy levels of MOs is not correct for all molecules. For e.g., for homonuclear diatomic molecules of second row elements in periodic table such as B₂, C₂, N₂, the s*2p_z molecular orbital is higher in energy than p2p_x andp 2p_y MOs. The order of MOs for such type of molecules is:

s1s, s *1s, s 2s, s 2s, p2P_x = p 2p_y, s *2p_z, p *2p_x = p *2p_y,

 s *2p_z.

Here the energy of molecular orbitals increases from s1s to s*2p_z.

But for molecules O₂ onwards (O₂, F₂), the first order of energies of molecular orbital is correct. Thus, for diatomic molecules of second period, there are two types of energy level diagram of Mos.

Conclusion for Molecular Orbital Energy

The main difference between the two types of sequences is that for molecules O₂, F₂ and Ne₂ the s2p_z, molecular orbital has lower energy than p2p_x and p2p_y MOs while in the case of molecules Li₂, Be₂, B₂, C₂ and N₂, s2p_z, molecular orbital is higher in energy than p2p_x and p2p_y MOs.

Electrochemical Impulses

Introduction:

Electrochemical impulses also called nerve impulses or action potential are conducted by specialized cells called neurons. All neurons conduct impulses along hair like cytoplasmic extensions, the nerve fibers or axons outside the central nervous system. A short-lasting event, in which the electrical membrane potential of a cell rises rapidly and falls, is known as an action potential.

In several types of animal cells, action potential occurs. These cells are called excitable cells which include neurons, muscle cells, and endocrine cells.

Function of Electrochemical Impulses:

In neurons, cell-to-cell communication is the major role of action potential. In other types of cells, activation of intracellular processes is their major function.

Mechanism of Electrochemical Impulses:

An action potential is the first step in the chain of events leading to contraction in muscle cells. They provoke release of insulin in beta cells of the pancreas. Special types of voltage gated ion-channels embedded in a cell's plasma membrane are responsible for generation of Action potential. When the membrane potential is near the resting potential of the cell, these channels are shut but they rapidly begin to open if the membrane potential increases to a precisely defined threshold value.

When the channels open, an inward flow of sodium ions is allowed, which changes the electrochemical gradient, which in turn produces a further rise in the membrane potential. This causes more channels to open, producing a greater electrical current. Until the entire ion channels are open, the process proceeds explosively leading to a large upswing in the membrane potential. The polarity of the plasma membrane gets reversed and the ion channels then rapidly inactivate because of the rapid influx of sodium ions.

As the sodium channels closes, it does not allow entry of sodium ions and they are actively transported out the plasma membrane. There is an outward current of potassium ions as potassium channels channels are activated, which returns the electrochemical gradient to the resting state.

Potassium Chloride Crystals

Introduction :

Potassium chloride crystals are the inorganic chemical compound, which is represented by the molecular formula KCl and the molar mass is 74.55g. Potassium chloride crystals is the salt of metal halide. Potassium chloride crystals are odorless and it is white in color and it is a crystalline solid.  The boiling and melting point of potassium chloride crystals are 1420°C and 770°C respectively. Potassium chloride crystals are soluble in water. Potassium chloride crystals have face centered cubic structure. Rarely potassium chloride crystals are known as muriate of potash.   It is toxic in excess if we intake orally.  It is hygroscopic in nature.  Potassium chloride crystal was discovered by Sir Humphrey Davy in 1807.

The appearance potassium chloride crystals is shown below,

              

Preparation and Structure of Potassium Chloride Crystals:

Preparation of Potassium chloride:
Potassium chloride crystals naturally occurs as sylvite, so potassium chloride is easily extracted from sylvinite.  It is obtained as a by-product in the preparation of nitric acid from hydrochloric acid and potassium nitrate. i.e.
KNO3 + HCl ===> HNO3 + KCl

Chemical properties of Potassium chloride crystals:

Potassium chloride crystals can react with silver nitrate to give silver chloride.
KCl + AgNO3 ==> AgCl + KNo3
Since potassium is more electropositive than sodium, so it is reduced to potassium metal
KCl (l) + Na (l) ⇌ NaCl (l) + K (g).

Structure of Potassium chloride crystal:
The structure o potassium chloride is face centered cubic.  The lattice constants are equal at 630 picometers .The potassium and the chloride ions are bonded through ionic bond.

Applications of Potassium Chloride Crystals:

Potassium chloride crystals have many applications; few of them are as below,

• Solution of potassium chloride crystals are used as strong electrolytes.
• They are used as good conductors of heat and electricity.
• In infrared and FTIR spectrophotometers, potassium chloride is commonly used as infrared transmission crystal windows in liquid and gaseous sample.
• It is used in preparation of fertilizers.
• It is also used in the manufacture of potassium metal and potassium hydroxide and also used as medicine.
• It is used as fire extinguishing agent.
• Like sodium chloride, it is used as flux for the gas welding of aluminium

Boyle’s law

Ideal gases are composed of rigid sphere molecules which are in random motion.  They can colloid with other molecules and wall of container. The collisions between molecules are completely elastic and due to this there is no loss of energy during collision. The average kinetic energy of molecules is directly proportional to temperature. All properties of ideal gas can be described by ideal gas equation given by;
PV = nRT

I like to share this Potential and Kinetic Energy with you all through my blog.

Ideal gas law is a combination of ideal gas laws which give relation between variables of gases like pressure, number of moles of gas, temperature and volume. Let’s discuss one of the laws known as Boyle’s law.

In 1626, Robert Boyle purposed a relationship between the pressure (p) and the volume (V) of a confined gas held at a constant temperature and for a constant amount.

Let’s first define Boyle’s law. According to Boyle’s law, the product of the pressure and volume is nearly constant at constant temperature and number of moles of an ideal gas. See what is Boyle’s

Law Formula from the given definition, it would be;
P x V = constant (at constant T and n)
Or P  ? 1/V

Boyle’s law can be written for two different volume and pressure;
P1V1= k = P2V2
Or P1V1= P2V2

Boyle’s law graph can be shown in two ways; P v/s V (hyperbola) and P v/s 1/V (linear). The
graphical representation of Boyle’s law is follow;

This law can only apply on an ideal gas not on real gases. The pressure and volume do not show same relationship on the compression of real gas. However this law is good enough to calculate the pressure and volume of internal-combustion engines and steam engines.

Boyle’s Law can explain by using Boyle’s law demonstration.  Let’s take a gas cylinder and put a piston on that for applying pressure on gas.  Keep this cylinder in water bath to maintain constant temperature throughout the experiment.  At initial stage; pressure of gas is 1 atm and volume is 8 ml. As we doubled the pressure that is 1 x 2 atm=2 atm, volume of gas becomes half; 8/2=4 ml.  Again the same thing observed as we double pressure, volume of gas becomes half.

It proves that at constant temperature and constant amount of gas, the pressure of gas is inversely proportional to the volume of gas.  This is because, as pressure on gas increases, the intermolecular space between molecules decreases and they come closer to each other.

For example; in a balloon as the pressure around a balloon are increases, volume of balloon decrease and vice-versa.

Check my best blog Balance equations.

Balance equations

A chemical reaction can represent by using a balance chemical equation.  A balance chemical equation shows reactant and product involve in given reaction with their chemical formulas. A chemical equation also represents, the phases of the participants (solid, liquid, gas) as well as the amount of each substance involve in reaction.

How to Balance a Chemical Equation: Chemical Equation Balancing is a step wise process. Let’s learn how to balance a chemical equation step by step.

1) First write the unbalanced equation by using chemical formulas of reactants and product.

2) Remember, of reactants are listed on the left hand side of the equation and Products on the right hand side.

3) One arrow is used to separated reactant and product to show the direction of reaction.

4) Balancing a chemical equation is based on the Law of Conservation of Mass which states that there are same numbers of atoms of every element on each side of the equation.

5) Balance all elements one by one on both sides by placing coefficients in front of them.

6) Indicate the phase of the reactants and products by using symbols like for use (g) for gaseous state, (s) for solids, (l) for liquids and (aq) for aqueous solution.

Balancing Chemical Equation Problems: For balancing a chemical equation practice, let’s do some problems;

Balance the given chemical equation; __KOH + __ H₃PO₄  __ K₃PO₄ + __ H₂O

Let’s start from first element ‘K’. Since there is one carbon on left side but three on right side, therefore for balancing ‘K’ put coefficient three on left side before KOH.

3KOH + __ H₃PO₄  __ K₃PO₄ + __ H₂O

Looking at the next atom (oxygen), the right hand side has seven atoms (three in KOH and four in H₃PO₄ , while the left hand side has five. To balance the oxygen, coefficient three goes in front of the H₂O;

3KOH + __ H₃PO₄  __ K₃PO₄ + 3H₂O

Now inspect next atom that is hydrogen, on right side there are six atoms and same number is on left side, therefore hydrogen atom is balanced on both side.
Inspection of the last atom to be balanced (phosphorus) shows that the right hand side has atom, similarly on the left hand side has one. Hence the balanced chemical equation can be written as

3KOH + H₃PO₄  K₃PO₄ + 3H₂O

Balancing Chemical Equation Practice

Some other examples of balanced chemical equation are as follow;

1. 2 Fe + 3H₂SO₄  Fe₂(SO₄)₃ + 3H₂
2. 2 C₂H₆ + 7O₂ 6 H₂O + 4CO₂
3. 4 NH₃ + 5 O₂ 4 NO + 6 H₂O
4. 1 B₂Br₆ + 6 HNO₃  2 B(NO₃)₃ + 6 HBr

Check my best blog Nitrogen Family of Elements.

Nitrogen Family of Elements

Introduction :

General information about the nitrogen family:
            Elements: ₇N, ₁₅P, ₃₃ As, ₅₁Sb, ₈₃ Bi
            Name: Nitrogen Family
            Electronic configuration:            ₇N = [He] 2s² 2p³
                                                               ₁₅P = [Ne] 3s² 3p³                                                                         
                                                               ₃₃As= [Ar] 3d¹⁰ 4s² 4p³
                                                                ₅₁Sb= [kr] 4d¹⁰ 5s² 5p³
                                                               ₈₃Bi = [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³
            In this article we shall discuss about the physical properties of nitrogen family of elements 

Physical Properties of Nitrogen Family:

• Atomic radii: they are smaller than the corresponding elements of group 14 because of increase in nuclear change. Down the group they show an increase mainly due to addition of a new shell.

• Oxidation state: Because of small size, N and P can gain three electrons to complete their octets and hence show an oxidation state of -3. Because of three half-filled orbital’s, they also show an oxidation state of +3. Except N, other elements also show an oxidation state of +5 because of the presence of empty d-orbital.

• Ionization enthalpy: IEs of these elements are much higher than the corresponding elements of group14 because of increase in nuclear charge and greater stability of exactly half filled orbitals. Down the group the values decrease because of increase in atomic size.

• Metalic: Metalic character increase down the group because of decrease in ionization enthalpy and increase in atomic size. Thus N and P are non-metals. As and Sb are metalloids while Bi is a typical metal.

Occurrence:
                       Molecular nitrogen comprises 78% by quantity of the impression. It occurs as sodium nitrate, NaNO₃ and potassium nitrate. It is founded in the form of proteins in plants and animals. Phosphorus occurs in minerals of the apatite family.Ca₉(PO)₆,CaX₂(X=F,C1 or OH) Which are the main components of phosphate rock.
Electronic configuration:
                       The valence shield electronic arrangement of these fundamentals is ns²np³. The s orbital in these element is completely filled and p orbitals are half filled.
Atomic and ionic radii:
                       Covalent and ionic radii increase in size down the group. There is substantial amplify in covalent radius from N to P. Bi only small increase in covalent radius is observed.
Ionization Enthalpy:
                       Ionization Enthalpy reduces down the collection due to gradual increase in atomic size. Because of the extra stable half-filled p orbital’s electronic configuration and small size. The ionization enthalpy of the group 15 elements is much greater than that of the group 14 elements in the corresponding periods.
Electro negativity:
                     Electro negativity value in group 15 general, decreasing down the group with increasing atomic size.
Physical properties:
                     All the element of this group 15 element is polyatomic. Dinitrogen is a diatomic gas while all other are solids. Metallic quality increases downward the collection.
Chemical properties:
                     The common oxidation state of these elements is -3, +3, and +5. The tendency to exhibit -3 oxidation state decreases downs the group due to increase in size and metallic character. The stability of +5 oxidation state decrease down the group.
In the case of nitrogen, all oxidation state from +1 to +4 tent to disproportionate in acid solution. 

Some other Physical Properties of Nitrogen Family:

• Electro-negativity: These are more electronegative than group 14 elements because of further decrease in size. It decreases down the group because of increase in atomic size

• Melting points and boiling points: Melting points first increase from N to As due to increase in nuclear charge and then decrease to Sb to Bi. The decrease is due to increase in size and weakening of inter atomic forces and also due to inter pair effect resulting in the formation of 3 bonds instead of 5.

• Nature of the bonds formed: N and P mainly from covalent bonds (through them also from N^3-  and P^3-). Down the group the tendency to from covalent bonds decreases i.e. the strength of the covalent bond decreases i.e the order is N > P > As > Sb > Bi

• Density: The densities increase regularly down the group as usual.

Organic Chemical Reactions

The term organic nowadays arouses lot of curiosity because of the term organic produce.

Whereas the meaning imbibed in this term relates to purity of agricultural produce  sans fertilizers or insectisides.
However in chemistry it applies to a wider term  that is connected to carbon.
Organic chemistry is the chemistry of carbon and its compounds, their preparations, physical and chemical  properties, reactions and everything about them.
The arena of this branch of chemistry has grown to such extent that a separate branch had to be earmarked for the study of these compounds.

Why Carbon?

Carbon is the important element to organic chemistry. But why?
It is because of the electronic configuration of carbon.
As it is having two 2p electrons, one 2p orbital is vacant and the valency of 4 can be obtained by carbon by the rearrangement of the orbitals.
As a result carbon can form single, double and even triple bonds with atoms like hydrogen, oxygen, nitrogen,etc.as well as other carbon atoms.
It can arrange itself in chained, cyclic, acyclic, branched and unbranched compounds.
It can even form hitherto unknown aromatic compounds where specific phenomena called resonance exists. In this type of structure as is in the benzene, the 3 pi bonds lie alternately in a aromatic ring.
This in turn facilitates nucleophilic as well as electrophilic additions to the aromatic ring.
Not only this, the s and p orbitals can mix up and get rearranged to give special 'hybridized' bonds like sp, sp2 and sp3.

Types of Organic Chemical Reactions

There are various types of organic chemical reactions. A few are as under.
Addition: It takes place across unsaturated double or triple bond.
e.g.CH₂=CH₂ + Cl₂   ---------------->  ClCH₂-CH₂Cl
Substitution When a species is substituted for another.
CH₃SH  + O₂    --> CH₃OH
Elimination When certain species is altogether removed.
ClCH₂-CH₃    ---------------> CH₂=CH₂ + HCl
Re-arrangement
When the compounds change the structure.
BrCH₂-CH₂ -CH₂Cl     <=======>  ClCH₂-CH₂-CH₂Br

Ether Nomenclature

Introduction:

The replacement of hydrogen atom in a hydrocarbon by an alkoxy group yields a new class of compounds known as ether. Ether is differing from the alcohols and phenols. Examples for ethers are as follows diethyl ether, methyl n-propyl ether, methylphenyl ether, ethylphenyl ether, heptyphenyl ether, methyl isopropyl ether and pheylisopentyl ether.          

Classification of Ether:

Based on the nomenclature property ether can be classified as two types.

Classification of ether:
Symmetrical ether
Unsymmetrical ether

Symmetrical ether:
Alkyl or aryl group attached to the oxygen atom are the similar is called as symmetric ether.
Example for symmetrical ether:
 Diethyl ether

Unsymmetrical ether:
Alkyl or aryl group closed to the oxygen atom are the different is called as unsymmetrical ether.

Example for unsymmetrical ether:
CH₃OC₂H₅

Nomenclature ether:
General name of ether is derived from the name of alkyl or aryl groups.
Example for ether with IUPAC name:
Common name                         IUPAC name
Dimethyl ether                         methoxymethane
Diethyl ether                           ethoxyetahne
Methyl n-propyl ether            1-methoxypropane
Methylphenyl ether                methoxypropane
Ethylphenyl ether                   ethoxybenzene
Heptyphenyl ether                  1-phenoxyheptane
Methyl isopropyl ether           2-methoxypropane  
Pheylisopentyl ether              3-methylbutoxybenzene

      According to IUPAC system of nomenclature, ethers are observed as hydrocarbon derived in which a hydrogen atom is swapped by an –OR or –OAr group, where R and Ar denotes the alkyl and aryl groups respectively. The huger (R) group is chosen as the parent hydrocarbon.

Properties of Ether Nomenclature:

Physical properties of ether:
      The C-O combinations in ethers are polar. Ethers contain net dipole moment. The weak polarity of ethers does not significantly affect their boiling points which are similar to those of the alkenes of comparable molecular groups.
The following ethers have the low level boiling point:
Ether name                      boiling point
N-pentane                              309.1
Ethoxyethane                        307.6
Butan-ol                                 390

Chemical properties of ether:
Cleavage C-O bond in ethers
Electrophilic substitution
Types of electrophilic substitution:

• Halogenations
• Friedel crafts reaction
• Nitration   

Molar Mass of Helium Gas

We use various units to measure the mass or weight of objects. We weigh our apples, oranges, vegetables and grains before buying them. It is easy to comprehend the idea of mass of a ball, apple or planet. There are different instruments for measuring the mass. However, can one place molecules of Helium gas on the grocer’s weighing balance and find how much they weigh?

What is the Molar Mass of Helium Gas

Molecular mass (MM), molecular weight (MW), formula mass (FM) or formula weight (FW) of a substance is the mass of a molecule of that substance. Here, we assume that every molecule that is composed of the same combination of atoms, will have the same mass. The unit of measure used is amu, which stands for atomic mass units.
One atom of carbon-12 (Carbon atoms with 6 neutrons and 6 protons) has a mass of 12 amu. This means 1 amu is about the weight of a neutron. It is evident that it is very small in magnitude. Atomic mass unit can also be expressed  in grams per mole (g/mol). One mole is the number of atoms in 12 grams of carbon-12. This number is called Avogadro's number or Avogadro's constant (N_A) and is equal to 6.022 x 10²³.
Sounds a little confusing? Let us do some math.
1atom of carbon - 12 = 12 amu
1 mole = no. of atoms in 12 g of carbon - 12, which happens to be 6.022 x 10²³ .
1 amu of an element = x g/mol  ( grams per mole - varies with each element).
This is the molar mass of the substance. It is the mass of one mole of the substance in grams, and not mass of one molecule.

Calculate Molar Mass

Helium occurs in natural form as a gas. It is a pure substance, i.e. an element in the periodic table.

One mole of helium atoms = 6.022 x 10²³ Helium atoms.
Number of atoms in m moles = m x  Avagadro’s constant = m x 6.022 x 10²³
So, 10 moles of helium (He) contains 10 x 6.022 x 10²³ = 60.022 x 10²³ helium atoms.
One mole of a pure element = molecular mass of the element.
One mole of molecules = Avogadro’s constant number of molecules.
So one mole of helium molecules =  6.022 x 10²³ molecules of helium.
Molecular mass of helium = Mass of one mole of helium molecules.
The question then is, how many grams of helium fit in one mole? This is the molar mass of Helium gas and happens to be 4.003 g/mol. (grams per mole of helium).

Uranium atomic symbol

Introduction :

Uranium atomic symbol is U.  Atomic number of Uranium is 92. Atomic Weight is 238.0289. Uranium is found in Actinide series and belongs to Radioactive Rare Earth Element. Uranium is discovered by Martin Klaproth.
It has Density of 19.05 g/cc, Melting Point 1405.5 K, Boiling Point 4018 K.
Uranium appears as Silvery-white, dense, ductile and malleable and it is a radioactive metal. 
Atomic radius of Uranium is 138 pm. 
Atomic Volume is 12.5 cc/mol. 
Electronic Configuration of uranium is [Rn] 5f³ 6d¹ 7s². 
Oxidation States of Uanium is 6, 5, 4, and 3.

Radiochemistry of Uranium:

Uranium Isotopes:
Natural uranium is 99.274 atom % ²³⁸U, 0.7205 atom % ²³⁵U, and 0.0056 atom % ²³⁴U. The 234/238 ratio is exactly the ratio of their half-lives as expected for nuclei in secular equilibrium. The isotope ²³³U is produced by neutron capture on ²³²Th, followed by β^- decay. ²³²U is a short-lived (t_1/2 =72 y) nuclide that is a contaminant in ²³³U samples (from fast neutron reactions). The daughters of ²³²U are hard gama-ray emitters that make working with 232U containing samples difficult. ^236,237,239U are produced by neutron captures on ²³⁵U and ²³⁸U. ²³⁶U is long-lived but ^237,239U are short-lived and decay to ²³⁷Np and ²³⁹Pu, respectively.

Metallic Uranium:
Metallic uranium can exist in three different solid phases with differing densities, depending on temperature.  At room temperature, a phase is observed with a density of 19.07 g/cm³ and a melting point of 1132^◦C.  Metallic uranium is a very reactive metal that is silvery in color. (Frequently, a surface oxide layer makes metallic uranium look black.) Uranium powder is pyrophoric. When uranium metal is cut or scratched in the laboratory, a shower of sparks is sometimes observed due to the creation of small particles that ignite. Uranium metal with an oxide coating will burn at 700^◦C to form U₃O₈. Uranium reacts with hot water to produce UO₂ and UH₃. In reactors, uranium is alloyed with zirconium to resist corrosion and radiation damage. Metallic uranium can be produced by the reduction of UF₄.

Uranium Compounds:

Uranium exists in the +3, +4, +5, and +6 oxidation states.  The +5 state disproportionate to the +4 and +6 states and is of little importance. Trivalent uranium reduces water and therefore there is no stable aqueous chemistry of U³⁺ although compounds do exist. The most important uranium compounds are the oxides. UO₂ is the compound used in reactor fuel. It is a stable refractory material that is brown-black in color and is nonreactive with H₂O.  Uranium hydride, UH₃, is a reactive black powder.  It is a powerful reducing agent and is pyrophoric.  A mixture of uranium and zirconium hydrides is used as the fuel.

Nitrogen Family

Introduction:
In periodic table elements are arranged in the ascending order of their atomic number.  They are arranged in such a way that elements with same electronic configuration fall under the same group.  As electronic configuration decides chemical property of an element, elements with in a group will have same chemical property.  Each group is called as a family with the name of the first element in that group.  Hence elements in the group under Boron are said to belong Boron family.  Similarly elements under the nitrogen are called as nitrogen family.

Position of Nitrogen Family in Periodic Table
In periodic table nitrogen family can be found in p Block elements.  Elements in which the valence electrons can be found in  p orbitals are called as p block elements.  They have general electronic configuration ns² np^1-6 . These elements occupy right corner of periodic table
  
Nitrogen family comes next to carbon in periodic table and this family consists of Nitrogen, phosphorus, Arsenic, Antimony and Bismuth

General Properties of Nitrogen Family:

This family elements have the general electronic configuration ns²,np³ . As the valence shell contains five electrons these elements have a maximum valency of five.
But as we move down the group of nitrogen family, the electrons in the S orbital will not take part in valency due to inert pair effect.  Thus elements in the bottom of the group will have a maximum valency of three.
As we down the group the atomic size increases and hence the metallic nature increases.  So Bismuth is metal while nitrogen is non metal
As the metallic nature increases the basic nature of the oxides increases.  So the Bismuth oxide is basic while nitrogen oxides are acidic

Inert Nature of Nitrogen:

In nitrogen family all other elements except nitrogen are highly reactive.  But nitrogen is chemically inert.  This is due to strong triple bond formed in molecular nitrogen.  But nitrogen is an important element in proteins and is required by animation for continuous survival.  Hence the nitrogen in atmosphere is fixed by nitrogen fixation to earth

Electro negativity and the periodic table

what is electronegativity ?
Electronegativity is the measure of the capacity of an atom of an element to attract the shared electron pair in a covalent bond towards itself.The electronegatiivty is different from the electron gain enthalpy in the sense that while electron gain enthalpy calculate the measure of attracting the electrons towards it self in the isolated gaseous state, the electronegativity measures the  power to attract the electrons pair in combined state.

The concept of electronegativity was introduced by Pauling in 1932,the trends of electronegativity in the periodic table is quite evident. In a period from left to right , the value of the electronegativity  increases while in a group from top to bottom , the value of electronegativity decreases.

For example :
Period 2nd   Li < Be< B< C< N<O<F 
Period 3rd   Na<Mg<Al<Si<P<S<Cl
Period 4th   K<Ca<Ga<Ge<As<Se<Br
Similarly  in group we find the electronegativity goes on decreasin from top to bottom:

for example :
Group 1A     Li>Na>K>Rb>Cs

Group  2A     Be>Mg>Ca>Sr>Ba  etc.
The electronegativity of an element is not constant and depends on the following factors:
1.State of hybridization : sp> sp2>sp3
2.Oxidations state of an element .Fe 3+> Fe2+.

In the periodic table the elements with low value of electronegativity are metals and with high values are non metals,the fluorine is the most electronegative element of the periodic table and the Cesium with lowest electronegativity.

Problems on Electronegativity Periodic Table

Question for practice :

• Question 1. Arrange the following elements in the decreasing order of electronegativity  :  F,Br,I Cl

Answer : as these are the halogens  or the elements of 7A group of the periodic table and as we know the electronegatiivty decreases down the group so the required order is F>Cl>Br>I

• Question2 .arrange the following in the increasing order of electronegativity : Na,Mg,K, Al,C,O ,F ,Cl

Answer : the required order is  K<Na<Mg<Al<Cl<O<F
NOTE : In periodic table the four most electronegative elements are  F>O >Cl >N.

Law of Conservation of Mass

Introduction

The law of conservation of mass is also termed as principle of mass/matter conservation. The law of conservation of mass states that mass cannot be created/destroyed, but it may be changed from one form to another. This concludes that for any chemical process in a closed system, the mass of the reactants must be equal the mass of the products.

Experiment for Law of the Conservation of Mass:

Discussion:

In this experiment, aqueous solutions of three different compounds will produce two separate and distinct chemical reactions. Balanced chemical equations for the two reactions are:

Na₂CO₃(aq) + CaCl₂(aq) ----2NaCl(aq) + CaCO₃(aq) (Eq.1)

CaCO₃(s) + H₂SO₄(aq) ------CaSO₄(s) + H₂O + CO₂(g) (Eq.2)

The combined masses of the three solutions will be measured before and after each reaction is completed.

PURPOSE

To recognize the law of conservation of mass and to determine the masses of reactants and products.

EQUIPMENT

Laboratory balance corks (to fit test tubes) (2), Erlenmeyer flask: 125-Ml, labels rubber stopper (for flask), safety goggles, and graduated cylinder: 10-mL, lab apron and coat test tubes 13 x 100-mm (2)

MATERIALS

1 M aqueous solutions of: Na₂CO₃, CaCl₂ and H₂SO₄

PROCEDURE

1. Measure exactly 10.0 mL of sodium carbonate (Na₂CO₃) solution in a graduated cylinder. Pour Na2CO3 into a clean, dry 125-mL Erlenmeyer flask. Stopper the flask.

2. Measure exactly 3.0 mL of 1 M calcium chloride (CaCl₂) solution by a pipette and pour into a clean, dry test tube. Put cork and label the tube.

3. Measure exactly 3.0 mL of 1 M sulfuric acid (H₂SO₄) solution by a pipette and pour into a clean, dry test tube. Put cork and label the tube.

4. Put the stoppered flask and the corked test tubes together on the pan of the laboratory balance. Tilt the test tubes to avoid liquids from touching the corks. Measure the total mass of these containers, stoppers, and solutions.

5. Now, remove the flask and the test tube containing the CaCl₂ solution from the balance pan. Pour the CaCl₂ solution into the Na₂CO₃ solution in the flask. Shake the flask to mix the two solutions thoroughly.

6. Replace the stopper and cork in their initial containers. Once again, measure the combined mass of the three containers, stoppers, and contents.

7. Remove the flask and the test tube containing H₂SO₄ from the balance pan. Pour the H₂SO₄ solution into the flask with care. Shake the flask until all bubbling stops. Note the readings.

8. Replace the stopper and cork and the solutions in their initial containers. Again measure the mass of the three containers, stoppers, and contents.

Result:

We will observe that the mass of the all three solutions will be conserved. Hence, this experiment proves the law of conservation of mass.

Molecules calculation

Mass of a molecule is sum of the masses of the constituent atoms.
The mass of an atom is sum of masses of neutrons and protons.
In turn, masses of certain number of molecules too would depend on the masses of the constituent atoms.
Using this logic, Avogadro devised a special term 'mole' which is a certain mass equivalent to the molar mass expressed in grams.

Introduction :

Avogadro was the first person to establish that elements exist as molecules.
Thus a mole can be defined as a certain number of molecules. This number was found out to be 6.022 x 10²³ molecules.
Thus a mole of oxygen, hydrogen, carbon dioxide, carbon monoxide or any substance would contain 6.022 x 10²³ molecules.
It can be further illustrated as under
If two moles of hydrogen combines with one mole of oxygen what is the number of molecules of water formed?
One mole= 6.022 x 10²³ molecules.
Two moles= 12.044x 10²³ molecules
                  2H₂            +                                O₂ ---------->                 2H₂O
12.044x 10²³ molecules + 6.022 x 10²³ molecules.---->          2 moles
So the answer is 12.044x 10²³ molecules of water. It may be mentioned here that it is not 2+1=3, as in mathematics.

Illustrations of Molecules Calculation

Let us consider a few problems.
Question 1;- How many molecules are there in 56 g of carbon monoxide?
Ans: First let us find the number of moles

number of moles = mass in gram/molar mass
=56/28
=2 moles
Now by Avogadro's hypothesis,
One mole of a gas contains 6.022 x 10²³ molecules.
so two moles would contain
2 x 6.022 x 10²³ molecules.
12.044x 10²³ molecules.

Question 2 :-
Find the moles in12.044x 10²³ molecules of hydrogen at STP.
Ans:  One mole of hydrogen = 6.022 x 10²³ molecules.
so 12.044x 10^23 /6.022 x 10²³ 
=2 moles
Question 3
A gas has volume of 44.8 L. What is the number of molecules in it?
22.4 L volume is occupied by one mole i.e. 6.022 x 10²³ molecules.
So, 44.8 L would be occupied by   6.022 x 10²³ x 2
= 12.0444 x 10²³ molecules.

Empirical and molecular formula

Introduction :

Empirical Formula

The empirical formula for a compound is the simplest ratio of the numbers of atoms of each element present in the compound, e.g. hydrogen peroxide H₂O₂, its empirical formula is HO.

Empirical formula mass of a compound: It refers to the sum of the atomic masses of the elements present in the empirical formula. We can calculate the empirical Formula using the composition of elements in a compound.

Find Molecular Formula

A molecular formula represents the number of atoms of each element in a molecule. Therefore, the multiples of empirical formula gives the molecular formula of a, e.g. hydrogen peroxide H₂O₂. The Molecular Mass (molecular weight) of a compound is calculated with the atomic masses of each element and times with the number of atoms present in a compound.

    Molecular formula mass = n x empirical formula mass

The Molecular formula shows each element by its chemical symbol and indicates the number of atoms of each element found in each molecule of that compound. For example, methane, a small molecule consisting of one carbon atom and four hydrogen atoms, has the chemical formula CH₄. The sugar molecule glucose has six carbon atoms, twelve hydrogen atoms and six oxygen atoms, so its chemical formula is C₆H₁₂O₆.

Examples of Empirical and Molecular Formula:

• Example 1: 

Common sugar: glucose

Ratio of carbon, hydrogen and oxygen are in the ratio of 1:2:1. So, the empirical formula is CH₂O.

Empirical formula mass of glucose: 12.0 + (2 x 1.0) + 16.0 = 30g/mol.

Molar mass or molecular weight of glucose is: 180.16g/mol 

Molecular formula mass = n x empirical formula mass

180.16g/mol = n x 30g/mol

n = 6

Therefore, the molecular formula for a compound is 6 x empirical formula, i.e.., 6 x CH₂O = C₆H₁₂O₆   

• Example 2:  Ethane 

Ratio of carbon, hydrogen and oxygen are in the ratio of 1:2. So,  the empirical formula is CH₃ 

Empirical formula mass is: 12.0 + (3 x 1.0) = 15.0 g/mol

Molar mass or molecular weight of  Ethane is 30.0g/mol 

Molecular formula mass = n x empirical formula mass

30.0 = n x 15.0

n = 2

Therefore, the molecular formula for a compound is 2 x empirical formula, i.e.., 2 x (CH₃) which is C₂H₆

Comparing Molecular and Empirical Formulas

Compound                                     Molecular formula                        Empirical formula

Water                                                 H₂O                                               H₂O

Hydrogen Peroxide                              H₂O₂                                              HO

Glucose                                             C₆H₁₂O₆                                        CH₂O

Methane                                            CH₄                                                CH₄

Ethane                                              C₂H₆                                              CH₃