Sun February 19, 2012 By: Mythrayee Balasubramanian

(a)How and (b)why do atomic radii of elements change as we move (1)from left to right in a period (2)down a group in the periodic table

Expert Reply
Sun February 19, 2012
It is a fundamental phenona. When we move from left to right in a period, at each step one more electron is being added to the atom. So, the atomic radii increases.
Similarly, when we move down the group. due to the incoming 8, 18 or 32 electrons, the atomic radius increases. 
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