Periodic Classification and Periodic Properties 2 Question 3
3. The correct option with respect to the Pauling electronegativity values of the elements is
(2019 Main, 11 Jan II)
(a) $\mathrm{P}>\mathrm{S}$
(b) $\mathrm{Si}<\mathrm{Al}$
(c) $\mathrm{Te}>\mathrm{Se}$
(d) $\mathrm{Ga}<\mathrm{Ge}$
(c) the first ionisation energies of elements along a period do not vary in a regular manner with increase in atomic number
(d) for transition elements the $d$-subshells are filled with electrons monotonically with increase in atomic number
Objective Question II
(One or more than one correct option)
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Answer:
Correct Answer: 3. (d)
Solution:
- The electronegativity values of given elements on the Pauling scale can be shown as follows:
| Period No. | Group 13 | Group 14 | Group 15 | Group 16 |
|---|---|---|---|---|
| 3 | $\mathrm{Al}(1.5)$ | $\mathrm{Si}(1.8)$ | $\mathrm{P}(2.1)$ | $\mathrm{S}(2.5)$ |
| 4 | $\mathrm{Ga}(1.6)$ | $\mathrm{Ge}(1.8)$ | $\mathrm{Se}(2.4)$ | |
| 5 | $\mathrm{Te}(2.01)$ |
On moving from left to right across a period, i.e. from $\mathrm{Ga}$ to $\mathrm{Se}$, the effective nuclear charge increases and size decreases.
As a result, the value of electronegativity increases due to increase in the attraction between the outer electrons and the nucleus. Whereas on moving down the group, (i.e. from $\mathrm{Se}$ to $\mathrm{Te}$ ), the atomic size increases.
As a result, the force of attraction between the outer electron and the nucleus decreases. Hence, the electronegativity decreases.
