Write the number of periods and groups in the Modern Periodic Table. How does the metallic character of elements vary on moving (i) from left to right in a period, and (ii) down a group? Give reason to justify your answer.

There are 7 periods and 18 groups in modern periodic table.


(i) Metallic character increases down a group because 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 loosing electrons increases. Hence metallic character increases down a group.


(ii) 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. Hence metallic character decreases from left to right in a period.


Note- Effective nuclear charge is defined as the charge per unit volume.


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