Na, Mg and Al 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? Justify your answer stating reason for each.

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Solution

1. Na has the largest atomic radii as compared to Mg and Al.
The atomic radius decreases when moving from left to right along a period. This is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.

2. Al is the least reactive. It has lesser tendency to lose electron due to high effective nuclear charge.

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