Question

write the number of periods in Modern Periodic Table state range in the valency and metallic character of elements as we move from left to right across a period also state the change is any in the valency and atomic size of elements as we move down a group

Answer 1

There are 7 periods in Modern Periodic Table

As we move across a period the valency increases when the metallic character decreases metallic character increases when we move down a group the valency remains same in a group while the atomic size increases down the group and the atomic size decreases across a period

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Answer 2

there are total 7 periods in modern periodic table
the valency of the element increases by 1 across a period
the valency does not change while moving down the group
the metallic character decreases as we go across the period