Question

Which of the following reason correctly justifies the magnesium has smaller atomic radius than sodium.
a. Mg and Na are in the same group.
b. Mg and Na are in same period.
c. Mg and Na are in the same period and across the period atomic size decrease from left to right.​

Answer 1

The element Mg and P are in the same period (third period) Thus P experiences more effective nuclear charge as the effective nuclear charge increases towards the right. Thus the size of Mg is larger as it has low effective nuclear charge. Hence the correct answer is option A.

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