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Question 33

The correct option with respect to the Pauling electronegativity values of the elements is:

First, we recall the empirical rule stated by Linus Pauling for his electronegativity scale: “Within one horizontal period of the periodic table the electronegativity generally increases from left to right, while within one vertical group it generally decreases from top to bottom.” We shall use this single qualitative rule repeatedly for every pair of elements appearing in the four options.

We start with Option A, the statement $$\text{Te} \; \gt \; \text{Se}.$$ Tellurium (Te) and Selenium (Se) both belong to Group 16 (the oxygen family). Moving down any group, electronegativity decreases because the atomic size increases and the effective nuclear attraction on the bonding electrons becomes weaker. Since Te lies below Se in the group, we must have $$\chi_{\text{Te}} \lt \chi_{\text{Se}}.$$ Hence the inequality written in Option A is reversed, so Option A is incorrect.

Next, we examine Option B, the statement $$\text{Ga} \; \lt \; \text{Ge}.$$ Gallium (Ga) is in Group 13 and Germanium (Ge) is in Group 14. Both are situated in the same fourth period. Across a period, from Group 1 to Group 17, the Pauling electronegativity increases because the nuclear charge rises while the addition of electrons occurs in the same principal shell, reducing atomic size and strengthening attraction for bonding electrons. Since Ge lies to the right of Ga within Period 4, we expect $$\chi_{\text{Ga}} \lt \chi_{\text{Ge}}.$$ The inequality in Option B is therefore perfectly consistent with the trend, making Option B correct.

Now we test Option C, the statement $$\text{Si} \; \lt \; \text{Al}.$$ Aluminium (Al, Group 13) and Silicon (Si, Group 14) both belong to Period 3. Applying the same left-to-right trend, we predict $$\chi_{\text{Si}} \gt \chi_{\text{Al}},$$ or equivalently, $$\chi_{\text{Al}} \lt \chi_{\text{Si}}.$$ Thus the given inequality in Option C is opposite to the actual one, making Option C wrong.

Finally, consider Option D, the statement $$\text{P} \; \gt \; \text{S}.$$ Phosphorus (P, Group 15) and Sulfur (S, Group 16) occur in Period 3. Moving from P to S in the same period, electronegativity should increase, so we must have $$\chi_{\text{P}} \lt \chi_{\text{S}}.$$ Again, the statement written in Option D reverses the true order, so Option D is incorrect.

From the detailed examination above, only Option B, namely $$\text{Ga} \lt \text{Ge},$$ agrees with the Pauling electronegativity trend.

Hence, the correct answer is Option B.

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