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Question:

Na, Mg, and Al are elements having one, two, and three valence electrons respectively. Which of these elements (i) has the largest atomic radius, (ii) is least reactive?

Solution:

  1. Na has the largest atomic radius 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 a lesser tendency to lose electrons due to a high effective nuclear charge.