. 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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