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.