Which is not correctly matched
(i) Basic strength Cs2O < Rb2O < K2O < Na2O < Li2O of oxides.
(ii) Stability of Na2O2 < K2O2 < Rb2O2 < Cs2O2 peroxides.
(iii) Stability of LiHCO3 < NaHCO3 < KHCO3 < RbHCO3 < CsHCO3.
(iv) Melting point NaF < NaCl < NaBr < NaI
(a) (i) and (iv)
(b) (i) and (iii)
(c) (i) and (ii)
(d) (ii) and (iii)
Correct answer: (a) (i) and (iv)
Explanation:
Basic strength of the oxides increases in the order Li2O < Na2O < K2O < Rb2O < Cs2O.
The increase in basic strength is due to the decrease in I.E. and increase in electropositive character.
The melting points of the halides decrease in the order NaF > NaCl > NaBr > NaI, as the size of the halide ion increases. The decrease in melting point is due to increase in the covalent character with increase in the size of anion according to Fajan's rule.