Important Conceptual Questions Group 15 Elements P Block Elements

Important conceptual questions group 15 elements P block elements 

Notes on important conceptual questions group 15 elements p block elements 

P Block Elements

 

P Block Elements

 

Here is the explanation of the notes in the video 👇

Important conceptual questions group 15 elements P block elements 

PCl5 is known but NCl5 is not known or nitrogen does not form pentahalides 

Phosphorus in the ground state has electronic configuration 3s2 3p3 and on excitation of 1 electron from 3s can be transferred to 3d energy level. After excitation 5 half filled orbitals are available in Phosphorus for the formation of PCl5

But in case of Nitrogen no 2s electron can be excited to higher energy level because it is thermodynamically unfavourable process so, NCl5 is not formed.

There is a difference between covalency and oxidation state in N2O5 

Covalency of Nitrogen in N2O5 is 4 and the oxidation state of Nitrogen in N2O5 is + 5

Stability of +5 oxidation State decreases down the group in group 15 of periodic table or tendency to form pentahalides decreases down the group 

Stability of of lower oxidation State that is +3 in case of group 15 elements increases down the group due to inert pair effect.

D and f electrons poor shielding effect so s electron pair is attracted more towards the nucleus with the increasing nuclear charge as we move down the group.

Reluctance of s electron pair to participate in bond formation is called is inert pair effect therefore only outer shell np3 electrons are available for bonding.

Bismuth is stronger oxidising agent in the pentavalent state.

Nitrogen and Bismuth does not form pentahalides while Phosphorus does. 

Nitrogen has no d orbitals to form pentahalides while Bismuth shows inert pair effect therefore both does not form pentahalides.

NH3 is more basic than PH3 

Ammonia is more basic than PH3 because of the small size of Nitrogen than phosphorus so, N-H bond is stronger than P-H

Nitrogen forms hydrogen bonding while chlorine does not inspite of having same electronegativity.

Due to bigger size of chlorine as compared to nitrogen, electron density per unit volume on nitrogen is higher than chlorine therefore nitrogen forms hydrogen bonding by chlorine does not inspite of having same electronegativity.

Dipole moment of NF3 is less than NH3 

Resultant of 3 N – F bonds opposes the dipole moment of lone pair in NF3 while the resultant of 3 N – H bonds adds to the dipole moment of lone pair in case of NH3 Therefore, dipole moment of NF3 is less than NH3 

Phosphorus shows greater tendency for catenation than nitrogen 

N – N bond is weaker due to smaller size of Nitrogen The lone pairs on 2 nitrogen atoms repel the bond pair of N – N bond so there will be less catenation for nitrogen than phosphorus

Ammonia acts as a ligand or good complexing agent 

Nitrogen in Ammonia has lone pair so it acts as a legand and combines with the transition metal cations to form complexes.

N2O5 is more acidic than N2O3 

N2O5 and and N2O3 dissolve in water to form HNO3 and HNO2. In nitric acid, the oxidation state of nitrogen is + 5 so, NO2 pulls the electron more strongly from.    O-H bond. Therefore, HNO3 releases H+ quickly.

In nitrous acid the oxidation state of nitrogen is +3 . Therefore  N2O5 can accept electrons more readily in comparison to N2O3

H3PO3 is diprotic ( dibasic ) or what is the basicity of H3PO3 

H3PO3 contains 2 ionizable hydrogen atoms which are present as OH groups therefore behaves as dibasic acid.

Nitrous acid can act as an oxidising agent as well as reducing agent 

In Nitrous acid oxidation state of nitrogen is + 3 Oxidation state of Nitrogen can be decreased to any lower value therefore, nitrous acid acts as oxidant or oxidizing agent. Oxidation state of Nitrogen can be increased to + 4 or + 5 therefore, it acts as reductant or reducing agent.

All bonds in PCl5 are not equivalent.

In PCL5 the axial bonds are less stable therefore PCl5 on heating dissociates into PCl3 and Cl2

Solid PCl5 exist as ionic in nature in the form of tetrahedral and octahedral units.

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