Atomic size

Introduction
 Let us discuss about the atomic size. According to modern the Atomic Theory, an atom is the minimum particle of an element which takes part in chemical reactions it maintains its identity all the way through every physical changes and chemical changes. Atoms of elements are quite reactive. They, therefore, normally do not exist in the free state except the atoms of noble or rare gases. Next we see the size of an atomic.

Atomic size

It has been found that the atoms of all elements are made up from three basic particles and that the atoms of different elements contain different numbers of these three particles. The particles are electron, proton and neutron. Since an atom has in general no charge, the many electrons external the nucleus is similar to the number of protons inside the nucleus. The even with microscope, they do not perceive them atoms are small.
               The atoms are generally declaring the building blocks of matter. They are very very small and do not be seen even by the majority of powerful microscope. An idea of the extremely small size of the atom can be had from the fact that 1cm of space can accommodate about 35,000,000 atoms arranged end to end in a line. The atomic radius is called as size of the atom is indicated by its radius. The atomic radius of the smallest atom, hydrogen is 0.37 x 10^-10 m or 0.037 nm. The nm is normally declaring the nanometer.
              The 1nm is normally declare the 1nm=10^-9 m or 10⁹ nm = 1 m. The small dimensions of hydrogen atom or atoms in general can be seen as compared with the size of some common objects given in the following table.

Relative sizes of some common objects

Relative sizes
Radii	Examples
10-1 m 10-2 m 10-4 m 10-8 m 10-9 m 10-10 m	Watermelon Ant Grain of sand A molecule of haemoglobin A molecule of water An atom of hydrogen

Mole Chemistry

You must hear about mole concept in chemistry that is basis of stoichiometry. Let’s first discuss what is a Mole in Chemistry? The amount of pure substance having the same number of atoms as in 12 grams of carbon-12 is known as one mole. In Chemistry Mole  is equals to 6.023 X 1023 or Avogadro number.

Now first question comes to your mind that what is a Mole? Mole definition states that the number of atoms in exactly 12 g of 12C is known as one mole. All stoichiometry is essentially based on the Mole Chemistry.

Amedeo Avogadro performed an experiment in 1811 and concluded that at the same temperature and pressure, equal volumes of gases contain equal numbers of molecules.

Hypothetically he purposed that number known as Avogadro number; 6.02 X 1023 or 602 000 000 000 000 000 000 000. Hence one mol of anything has 6.02 x 1023 particles such as one mole of silver contains 6.02 x 1023 atoms of silver.

Let’s take a simple example of calculation of mols present in compound such as water. A of mol of water contains 6.02 x 1023 molcules weighs 18 gm. Hence a mol is a collection of atoms with a mass equal to the atomic weight in grams.

Mole of an element is directly related to atomic weight or atomic mass formula of that element. For example; the atomic weigh of lithium is 6.941amu, it means 6.941 grams of lithium contains 6.02 x 1023 atoms of lithium.

The mole concept can be used for the relation between the number of particles and the mass of a substance. Let’s do an example for that. Calculate the number of atoms present in 0.24 mol of sodium. As we known, in one mole of sodium there are 6.02 × 1023 atoms. Therefore in 0.24 mols of sodium contain 0.24 x 6.02 × 1023 = 7.22 x 1022 atoms of sodium.
The best way to express the atomic mass of any substance in grams is known as molar mass. The only change is in their units. Such as the atomic mass of iron is 55.85 amu and molar mass is 55.85 g/mole. For diatomic molecules the molar mass units is just double to its atomic mass. Like the molar mass of oxygen is 32.00 g/mol and atomic mass is 16.00 amu. The molar mass of polyatomic compounds is the sum of molar mass of each atom. Let’s calculate the molar mass of magnesium nitrate, Mg(NO3)2 is sum of atomic mass of Mg, 2N and 6O.
Molar mass of Mg(NO3)2 = 24.31 + 2(14.01 + 16.00 + 16.00 + 16.00)
=24.31 + 2(62.01) = 148.33
The relation between molar mass, mol and number of particle can be written as;
6.02 × 1023 particles = one mol = molar mass

Laws of Thermodynamics

Keywords

The Second Law of Thermodynamics

The Zeroth Law of Thermodynamics

Second Law Thermodynamics

Second Law of Thermodynamics Examples

There were some phenomenon and concepts observed by scientist which cannot explain by using the zeroth law of thermodynamics and 1^st law. As necessity is the mother of discovery so it developed the second law of thermodynamics.

There are many formulations and applications of the 2^nd Law. To understand the law, batter to take some second law of thermodynamics problems like production of heat in a heater after passing the current (work) a wire (resistance).

Electricity (work) heat

Therefore as per first law of thermodynamics;

Q = W

But this law does say anything about the direction of the energy transfer. It means we can reverse the process to produces electricity by passing heat.

However, we know it’s not possible practically. So there must be some kind of directions followed by process.

Let’s take another example to understand Second Law Thermodynamics. Take a cold can of soda and placed in a warm room. According to 1^st law, heat will be transferred from surroundings to the soda. As system is in no motion, so work done will zero and Q will be positive as system is absorbing some energy.

But we cannot say anything for reverse process, transfer of energy to room and decreases the temperature of soda can. No doubt, from various experiments and everyday life, we know that heat can only transferred spontaneously from a warm system to cold one.

Now to understand the direction of various processes, there are two statements given by Clausius and Kelvin are as follows;

1. There is no such type of process, in which heat transferred from low temperature to high temperature.
2. In any thermodynamic process, the absorption of heat from a reservoir cannot convert completely into work.

There are generally two cycles studied for 2^nd law;

1. Heat engine: Converting heat to net work.
2. Refrigerator: transfer heat from low temperature to high temperature medium.

In both cycles; there is a thermal reservoir which can supply or absorb heat without changing temperature. The thermal reservoir with high temperature is called as source and with low temperature, known as sink. In a thermodynamic cycle, source can supply heat to the system and sink can absorb heat.

A heat engine receives heat from a high temperature source and a fraction of the heat converted into work. The remaining heat rejected to a low temperature sink.

According to 1^st law of thermodynamic; Q_NET = W_NET

While from 2^nd law; Q _out>0

Efficiency of heat engine can give by; η= W_net/Q_input

or η= Q_input –Q_output /Q_input

Check my best blog Law of Octaves.

Law of Octaves

To know the Law of Octaves, we must first know what an Octave is?

Lets us now Define Octave: It could be defined as arrangement of eight note occupying the interval between two notes, wherein, one having twice or half the frequency of vibration of the other.

For example: In musical notes, after certain interval the note will repeat itself.

1	2	3	4	5	6	7
Sa	Re	Ga	Ma	Pa	Dha	Ni
Sa	Re	Ga	Ma	Pa	Dha	Ni

Now let us discuss Law of Octaves: It was proposed in the year 1865 by John Newlands (John Alexander Reina Newlands), British chemist, who classified the elements based on his law. According to the law, when elements placed in an increasing order of their atomic mass formula, every eighth element will show similarity in both physical and chemical properties. Since Newland proposed the Law of Octaves, in his honor the law is also called as Newlands Octaves.

We shall now study the Newlands Periodic Table; based on his law, Newlands arranged the known elements in a tabular form, wherein even row consists of seven elements and the eighth element was placed under the first element.

For example: The Newlands Periodic Table symbols is shown bellow, where in the lithium (Li) is the first element and the sodium (Na) is the eighth element, the Li and Na exhibit the similar physical and chemical properties, similarly, if we start arranging the elements in the increasing order of their atomic mass from Beryllium (Be) then the eight element would be Magnesium (Mg), both will exhibit similar chemical and physical properties.

Li	Be	B	C	N	O	F
Na	Mg	Al	Si	P	S	Cl
K	Ca

Newlands Periodic Table

Now we shall look into the drawbacks of the Newlands Octaves:

• The law does not hold good for the elements having atomic masses higher than calcium.
• Noble gases does not obey this law
• Classification was based on the atomic mass of an element is the periodic function of its chemical and physical properties concept.
• The law was valid till the Henry Moseley (1913), put forth the concept that the properties of an elements varies periodically according to the atomic number but not to the atomic mass. 

Carbon's position in the periodic table

Introduction :

Carbon is the element which is very important from the ancient times. It was found in the form of soot and charcoal and etc. It is also found in nature in various forms like petroleum, coal and CaCl₂ and magnesium carbonate. Carbon is also found in most of the foods which we used to daily in real life.

Carbon element is very reactive and found in both states i.e. in Free State and combined states. It is found in both forms such as amorphous and crystalline in Free State. Most common crystalline forms of carbon exist in nature are graphite and diamond. In the nature, the amorphous form of carbon does not exist. This amorphous form is made from organic material while some are manmade. This form is present as carbon dioxide present in air, coal, hydrocarbons like methane, natural gas etc, and proteins, carbohydrates and vitamins in the living organisms.

Carbon in Periodic Table:

The symbol of carbon element is C. It has atomic number of 6 having mass number 12. The three isotopes of carbon are:
¹²C₆, ¹³C₆ and ¹⁴C₆

1. The first element of IV A group is Carbon.

Properties of Carbon due to Ots Position in the Periodic Table:

The electronic configuration of IVA group shows that the members of this group have four electrons in the outer orbit.

Apart from carbon element, there are four other elements present in this group. They are silicon (Si), germanium (Ge), tin (Sn) and lead (Pb).

As we know, the carbon is  non-metal in nature. However if we go down in group IV A, the metallic character of this group’s elements increases.

Thus we can say that C and Si are non metals. Ge is metalloids and Sn, Pb are metals.

The elements of IV A group also have allotropy forms. For example carbon is found as graphite, diamond and coal etc.

The most important property of carbon is that it can form bonds with carbon itself which create the chain of carbon. This characteristic or property is termed as catenation. The carbon is the element which shows maximum catenation. Silicon shows this property to little extent and other elements of this group do not have catenation.

Likewise silicon exists as amorphous and crystalline forms.

The element carbon has tetra valency. With monovalent atoms, carbon can forms four single bonds.  For example: CCl₄

Formula for carbon tetrachloride

Introduction  :

Carbon tetrachloride is an organic compound , consists of two elements carbon as well as chlorine , which has the formula `C Cl_4`and having the IUPAC names as tetrachloromethane.
                                                                              
CHEMICAL FORMULA  :- `C Cl_4`
In the carbontetrachloride molecule four chlorine atoms are arranged in a tetrahedral way with carbon atom in the centre which makes it non polar in nature. A 3-d view of the carbontetrachloride molecule is shown as under:
                                          

Preparation of the Carbon Tetracloride :

Carbon tetrachloride can be prepared by the following three methods , we can prepare by any one of them.
1. By combining one molecule of methane with four molecules of chlorines , we get carbon tetrachloride as well as hydrogen chloride. Below is the reaction
         CH₄ + 4 Cl₂ → CCl₄ + 4 HCl
2 . By chlroination of carbon disulphide , we get carbon tetrachloride as well as sulphur monochloride .Below is the reaction
       CS₂ + 3Cl₂ → CCl₄ + S₂Cl₂
3. By the syntesis of the dichloromethane , we get two molecules of carbon tetra chloride    

C₂Cl₆ + Cl₂ → 2 CCl₄

Features and Uses of Carbon Tetrachloride :

• It has a boiling point of `76.7^o` C
• It is not able to dissolve iodine.and  non-polar in nature.
• It is a colourless liquid which is soluble with nearly mostly other liquids but is slightly soluble with water.
• Used in refrigerants, flour bleachings .
• It is a very good fire extinguisher as well as a dry cleaning liquid.
• Also used in pharmaceutical materials preparation.
• Used in lava lamps , used as a source of chlorine in organic chemistry.
• High use of carbon tetrachloride in open environment can effect the health also , lead to  kidney problems , liver problems , also led to the degradation of the nervous system.

Carbon Compounds

Introduction :

Carbon compounds play an important role in our daily life. Every living organism possess hydrocarbons. We cannot think of living life without carbon compounds. Carbon compounds with single bond between two carbon atoms are called alkanes and with triple bond are called alkynes e.g. ethane, ethene and ethyne. Apart from carbon and hydrogen, hydrocarbons also contain other elements, namely oxygen, nitrogen and sulphur etc.
The basic carbon compounds are - alkanes, alkenes and alkynes. Let us describe each of them:

Alkanes - Alkanes are also known as saturated hydrocarbons. In alkanes, the hydrogen and the carbon atoms are joined using the single bond. The simplest alkane is CH₄ or methane, which is as shown below. Examples of larger alkanes are waxes and saturated oils.

Alkanes are acyclic molecules. It is saturated. They are not very reactive.
Alkenes - An alkene is an unsaturated carbon compound. It contains atleast one carbon-carbon double bond. The general formula for alkenes is C_nH_2n. Example of the simplest alkene is Ethylene (C₂H₄).

Alkynes - These hydrocarbons have a triple bond between two carbon atoms. The general formula for alkynes is C_nH_2n-2. Alkynes seem to be more reactive, but are hydrophobic. They are also known as acetylenes.
Group of atoms in a structure that determines the characteristic reactions of a compound is called functional group. Few important functional groups are:
a) Alcohol
b) Aldehyde
c) Ketone
d) Carboxyl
e) Ester
Let us learn the naming of some of the carbon compounds:

Naming of Alcohols:

Alcohols are hydroxy derivatives of alkanes. When one hydrogen atom of alkane is replaced by a -OH group then formation of alcohol takes place. Alcohols are also called as alkanols. Alcohols have general formula C_nH_2n+1OH.
Alcohols are homologous series of compounds that contain - OH functional group. While naming alcohol letter 'e' from homologous series of alkane is replaced by 'ol' as shown:
Alkane                                                                                    Alcohol
Methane                                                                                 Methanol
Ethane                                                                                    Ethanol
Propane                                                                                  Propanol
When more than two carbon atoms are present in a carbon compound then while writing the name of a compound the position of carbon atoms is also specified.
E.g. CH₃ - CH₂ - CH₂OH      Propan -1 -ol

Naming of Carbonyl Compounds:

Aldehydes and ketones represent a family of organic compounds known as carbonyl compounds.

Naming of Aldehydes:
While naming aldehydes the letter 'e' of corresponding homologous series os alkane is replaced by 'al' as shown:

Alkane                                                                           Aldehyde
Methane                                                                        Methanal
Ethane                                                                           Ethanal
Propane                                                                         Propanal

Naming of Ketones:
While naming ketones, the letter 'e' of corresponding homologous series of alkane is replaced by 'one'.
E.g. The simplest ketone is acetone and IUPAC name is propan-2-one.
Few more members of ketone series are: Butan - 2 -one, Pentan - 3 - one etc.

Naming of Carboxylic Acid:

Carboxylic acids are homologous series of compounds having -COOH group. While naming carboxylic acids the letter 'e' of corresponding homologous series of alkanes is replaced by 'oic' as shown:
Alkane                                                                                            Carboxylic Acid
Methane                                                                                          Methanoic Acid (Formic Acid)
Ethane                                                                                             Ethanoic Acid
Propane                                                                                           Propanoic Acid