Answer the following :
(a) Why inert gases are monoatomic ?
(b) Comment on 'Iodine possesses some metallic lusture'.
(c) Of all noble metals, gold `(Au)` has a relatively high `EA`. Explain.
( d) `Cl` and be converted to `Cl^(ɵ)` ion easily than `F` to `F^(ɵ)` ion. Explain.
(e) Why `Al(OH)_(3)` is amphoteric in nature ?

Explanation

(a) Inert gas has completely filled orbitals `(ns^(2) np^(6))` and so does not form bonds.
(b) `K(4s^(1))` has low `IE` and thus possesses strong tendency to lose electron and show strong metallic nature. Whereas `Cl(3s^(2) 3p^(5))` possesses high `EA` and thus show more tendency to accept electron and show non-metallic character.
( c) Metals have low `IE` and so valence electrons form an ocean of loosely bonded electrons. These looosely bonded electrons are reposible for conduction of current in metals.
(d) `I_(2)` is a violet crystalline solid having metallic lusture and forms ionic compounds like `(CH_(3)COO)_(3)I` in which it forms `I^(3+)` ion.
(e) Due to imperfect (or poor) shielding effect by the inner `4f` and `5d` orbitals, the `Z_("eff")` is increased which increases the attracting ability of incoming electron and hence it has high `EA` value (i.e. more negative value).
Electronic configuration of `Au (Z = 79)` is
`Au rArr 1s^(2), 2s^(2) 2p^(6) 3s^(2) 3d^(10) 4s^(2) 4p^(6) 4d^(10) 4f^(14) 5s^(2)5p^(6)5d^(10)6s^(1)`
(f) N/A
(g) Because `EA` of `Cl gt F`.
(h) Because both `Al-O` and `O-H` bond dissociation energies are comarable and hence both can undergo dissociation imparting amphteric nature.
(i) N/A
(j) `K_((g)) rarr K_((g))^(o+) e^(-), IE_(1) = x kJ mol^(-1)`.
`K_((g)) rarr K_((g))^(o+) e^(-), IE_(1) = x kJ mol^(-1)`.
`K_((g))^(o+) + e^(-) rarr K_((g)), EA_(1) = -x kJ mol^(-1)`.
`K_((g))` is converted to `K_((g))^(o+)` by giving `IE_(1)`. In order to go back to its original state, it will liberate energy equal to `x kJ mol^(-1)`, and this called `EA`. (`IE` and `EA` of the same element are equal in magnitude).
(k) The radii of noble gases are van der Waals radii which are larger than both ionic and covalent radii which is shown by other atoms.