Physical Properties of group 15:
- Electronic configuration of group 15 members: general electronic configuration is ns2np3.
- Nitrogen (N) [He]2s2,2p3
- Phosphorous (P) [Ne]3s2,3p3
- Arsenic(As) [Ar]3d10,4s2,4p3
- Antimony (Sb) [Kr]4d10,5s2,5p3
- Bismuth (Bi) [Xe]4f14,5d10,6s2,6p3
- Atomic size: As compared to group 14 they are smaller in size due to increased nuclear charge.
Along group, size increases as every time a new shell is being added due to which nuclear charge decreases.
- Ionization energy: The group 15 has high ionization energy than group 14 because of smaller size.
Along group, ionization energy decreases as size increases
- Electro negativity: Because of smaller size the group 15 members re more electronegative than group 14. Out of them the increasing order of electro negativity is:
- Metallic character: They are less metallic than group 14 because of small size and increased nuclear charge.
Along group metallic character increases as size increases and ionization energy decreases. The order of their metallic character is: N<P<As<Sb<Bi
- Melting point and boiling point: The melting point depends upon the type and number of bonds formed whereas boiling point depends upon Vander wall force which increases in magnitude with increase in size.
- Boiling points: It increases down the group as size increases. The order is – N<P<As<Sb<Bi
- Melting point: It first increases then decreases.
The order is: N<P<As>Sb>Bi
The reason for this decrease in case of antimony and bismuth is due to use of only three electrons out of 5 in bond formation because of inert pair effect.
- Catenation : They show only up to small extent like P exist as P4
Nitrogen as N2.
- Oxidation states: They have configuration ns2np3. Their common oxidation states are +5 and +3.
The oxidation states shown by them are:
- Nitrogen shows: -
- -3 (Ca3N2) Calcium Nitride
- -2 (NH2NH2) pyridine
Also show +3.
-3 (Ca3P2) Calcium Phoshide
- Bismuth: as +3 due to inert pair effect. It has only one compound in +5 oxidation state that is BiF5 (Bismuth pentafluoride).
Please note: Nitrogen do not form compounds in +5 oxidation states because:
- It has no vacant d orbital therefore no excitation can occur. So, maximum covalence shown by it is 4.
Anomalous behavior of nitrogen:
- It has small size
- It has high ionization energy
- It is most electronegative
- It has no vacant d orbital
- In it no dπ-pπ bonding can occur.