Question

. Write the number of periods the modern periodic table has. How do the valency and metallic character of elements vary on moving from left to right in a period? How do the valency and atomic size of elements vary down a group? (cbse 2013

Answer 1

the number of periods in modern periodic table is 7.when we move from left to right metallic characters decrease and non metallic characters increase.when we move from up to down metallic characters increase whereas non metallic character decrease. When we go left to right in a period the atomic size reduces. when we move from up to down ina group the atomic size increases.

the valency of group 1 is 1

the valency of group 2 is 2

the valency of group 13 is 3

the valency of group  14 is 4

the valency of group 15 is 2 or 5

the valency of group 16 is 2

the valency of group 17 is 1