. Justify your answer stating reason for each
Na, Mg and AI are the elements having one, two and three valence electrons respectively. Which of these elements (i) has the largest atomic radius, (ii) is least reactive
Best Answer
Ans. Na, Mg and Al are the elements of same period where Na is the first, Mg is the second and Al is the third member.
(i) Na has the largest atomic radius because on moving from left to right in a period, the atomic radius of elements decreases. As we move from left to right in a period, the atomic number of elements increases and the extra electrons are added to the same shell. Due to large positive charge on the nucleus, the electrons are pulled in more close to the nucleus and the size of the atom decreases.
(ii) Sodium is very reactive, Mg is less reactive whereas Al is still less reactive because on moving from left to right in a period, the chemical reactivity first decreases and then increases.
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