Question

difference between periods and groups​

Answer 1

hey

According to modern periodic table

periods :- These are horizontal columns and are 7 in number

groups :- These are vertical rows and are 18 in number

Answer 2

Horizontal rows present in periodic table are called as periods which are 7 in number. Each element of particular period has same number of shells.

vertical columns present in periodic table are called Groups which are 18 in number. Each element of particular group has same valency.