How does the tendency of the elements to lose electrons change in the Modern Periodic Table in

a. a group


b. a period and why?

(a) Since the size of elements increases down a group due to increment in the shells. So the effective nuclear charge decreases down a group. Due to this effective nuclear charge, the electronegativity decreases and the attraction of nucleus on valence shell electrons also decreases. So the tendency of the elements to lose electrons increase down a group.


(b) From left to right in a period, the effective nuclear charge increases because charge increases from left to right due to increment of proton. But the size remains same because number of shells remains same from left to right in a period. Due to this effective nuclear charge, the electronegativity increases and the attraction of nucleus on valence shell electrons also increases. So the tendency of the elements to lose electrons decreases.

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