Q14 of 56 Page 1

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.

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, Mg and Al belongs to the same period in which Na is the first element, Mg is the second element and Al is the third element. As we move from left to right, the atomic size of the elements decreases due to increase in the atomic number of the elements and addition of extra element in the subshell. Addition of Na has largest atomic radius.


(ii) On moving from left to right in a period, chemical reactivity is increased first and then decreased afterwards. So, Sodium is the least reactive among Na, Mg and Al.


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