CUCICISES
1 Discuss the general characteristics of Group 15 elements with reference to
their electronic configuration, oxidation state, atomic size, ionisation enthalpy
and electronegativity.
Answers
Answer:
The general electronic configuration of 15th group elements is ns2 np3. The number of valence electrons present is 5.
(b) Oxidation state:- Since the number of valence electrons is 5 so it needs 3 more electrons to complete the octet. Thus the general oxidation state is +3 and +5.
(c) Atomic size:- As a general trend, on moving down the group atomic size increases due to the increase in the number of shells.
(d) Ionisation enthalpy and electronegativity:- Due to the increase in size ionisation enthalpy as well as electronegativity decreases as we move down the group.
Nitrogen family
(Group 15 Elements)
7 (N) = 1s^2 2s^2 2p^3
15 (P) = 1s^2 2s^2 2p^6 3s^2 3p^3
33 (As) = 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^3
51 (Sb) = 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 4d^10 5s^2 5p^3
81 (Bi) =1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 4d^10 5s^2 5p^6 4f^14 5d^10 6s^2 6p^3
Nitrogen family elements are also known as Pnicogens.
General Electronic Configuration of Group 15 Elements = ns²np³
Oxidation state: N to Bi electro-negativity decreases. So, tendency to show -3 oxidation state also decreases. That's why after N, they show oxidation if +3 and +5.
[Atomic Size: Down the group number of electrons increases. So, shells also increases. Due to this atomic size increases.]
Atomic Radii: Radii of N-family smaller than the C-family, because along with the period nuclear charge increases. So, electrons are more strongly attracted towards nucleus. This results in decrease in shielding or screening effect.
But down the group Atomic Radii increases because of increase in shielding or screening effect.
Ionisatiom Energy/Enthalpy: Down the group Ionisation Energy decreases because of increase in size. So, force of attraction decreases.
Electronegativity: Down the group electro negativity decreases because of increase in Atomic Radii.