Ncert Solutions Chemistry Class 11th

(a) The element V has the highest first ionization enthalpy (? _iH₁) and positive electron gain enthalpy (? _egH) and hence it is the least reactive element. Since inert  gases have positive? _egH, therefore, the element-V must be an inert gas. The values of? _iH₁,  ? _iH₂ and? _egH match that of He.

(b) The element II which has the least first ionization enthalpy (? _iH₁) and a low negative electron gain enthalpy (? _egH) is the most reactive metal. The values of ? _iH₁,  ? _iH₂ and? _egH match that of K (potassium).
               

(c) The element III which has high first ionization enthalpy (? _iH₁) and a very high negative electron gain enthalpy (? _egH) is the most reactive non-metal. The values of? _iH₁,  ? _iH₂ and? _egH match that of F (fluorine).
               

(d) The element IV has a high negative electron gain enthalpy (? _egH) but not so high first ionization enthalpy (? _egH). Therefore, it is the least reactive non-metal. The values of? _iH₁,  ? _iH₂ and? _egH match that of I (Iodine).
               

(e) The element VI has low first ionization enthalpy (? _iH₁) but higher than that of alkali metals. Therefore, it appears that the element is an alkaline earth metal and hence will form binary halide of the formula MX₂ (where X = halogen). The values of? _i H₁,  ? _iH₂ and? _egH match that of Mg (magnesium).
               

(f) The element I has low first ionization (? _iH₁) but a very high second ionization enthalpy (? _iH₂), therefore, it must be an alkali metal. Since the metal forms a predominantly stable covalent halide of the formula MX (X = halogen), therefore, the alkali metal must be least reactive. The values of? _iH₁,  ? _iH₂ and? _egH match that of Li (lithium).