The first (Δ_i H₁) and the second (Δ_i H₂) ...

NCERT Class XI Chemistry Classification of Elements and Periodicity in Properties Solutions

Question : 31 of 40

Marks: +1, -0

The first

(\Delta_i H_1)

and the second

(\Delta_i H_2)

ionization enthalpies (in

\mathrm{kJ\,mol}^{-1}

) and the

(\Delta_{eg} H)

electron gain enthalpy (in

\mathrm{kJ\,mol}^{-1}

) of a few elements are given below :

Elements	$\Delta H_1$	$\Delta H_2$	$\Delta_{eg} H$
I	520	7300	–60
II	419	3051	–48
III	1681	3374	–328
IV	1008	1846	–295
V	2372	5251	+48
VI	738	1451	–40

Which of the above elements is likely to be :

(a) the least reactive element

(b) the most reactive metal

(d) the least reactive non-metal

(e) the metal which can form a stable binary halide of the formula

\mathrm{MX}_2

(X = halogen)

(f) the metal which can form a predominantly stable covalent halide of the formula MX (X = halogen)?

Solution:

(a) V : The element V has highest first ionization enthalpy and positive electron gain enthalpy hence, it is least reactive.

(b) II : The element II has the least first ionization enthalpy hence, it is most reactive metal.

(d) IV : Element IV has high negative electron gain enthalpy but ionization energy is not that high hence, it is least reactive non-metal.

(e) VI : The first and second ionization energies of element VI indicate that it can form a stable binary halide.

(f) I : The element I has very low value of first ionization energy but very high second ionization energy. Hence, it will form a stable covalent halide of the formula MX.

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