Question

How many groups and periods are there in the modern periodic table ? How do the atomic size and metallic character of element vary as we move:a}down a group and b}from left to right in a period

Answer 1

There are 18 groups and 7 periods in a periodic table.
Down a group:
-> Atomic size increases
->Metallic character (electropositivity) increases
Across a period(left to right):
->Atomic size decreases across a period
->Metallic character (electropositivity) decreases

Answer 2

Number of groups -- 17
Number of periods -- 7

a) When we move down the group the atomic size increases because the distance between outermost electrons and nucleus increases.

When we move down the group the metallic character of element increases because the effective nuclear charge decreases hence the ability to lose electrons increases.

b) When moving left to right in a period the atomic size of element decreases because there is an increase in nuclear charge which pulls the electrons closer to nucleus thus reducing its radius.

When moving left to right in a period the metallic character of an element decreases because the effective nuclear charge increases thus the element loses it ability to lose electrons easily

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