Question

Assign reasns for the following
(i) Sulphur vapour is paramagnetic,
(ii) Ammonia `(NH_(3))` has greater affinity for protons than phosphine `(PH_(3))`.
(iii) The negative value of electron gain enthalphy of fluorine is less than that of chlorne.
(iv) `SF_(6)` is much less reactive than `SF_(4)`.
(v) Of the gases only xenon is know the form well-established chemical compounds

Answer 1

(i)In vapour state sulphur partly as `S_(2)` molecule which has two unpaired electrons in the antibonding `pi^(**)` orbtitals like ` O_(2)` and hence it exhibits parmagnetism
(iii) When `NH_(3) or PH_(3)` accepts a proton, and addtional N-H or P-H bond is formed
`H_(3)N:+H^(+)rarrNH_(4)^(+) and H_(3):+H^(+)rarrPH_(4)^(+)`
Due to the bigger size of P than, N, than P-H bond is weaker .As a result `PH_(3)` has less tendency than `NH_(3)` to accept a proton. Therefore, `NH_(3)`, has higher proton affinity than `PH_(3)`
(iii) The electron gain enthalphy of flurin is less negative than that of chlorine due to that there is strong repulsion of electrons
(iv)In `SF_(6)` sex F atom protect the sulphur atom from attack by the reagent to such adn extent tht enven thermodynamically msot favourable reaction like hydrolysis do not occur.
Nut in `SF_(4)`,is not sterically protected sicne ist is surrounded by only four F atoms, hence `SF_(4)`, undergoes hydrolysis
(v) Exepct radon which is radioactive Xe has least ionisation energy among noble gasses and hence it is readity forms chemical compounds particularly with oxygen and flurine.