Question

Find the period and group of the element whose atomic number is 20

Answer 1

The element is Calcium...

Its period number is 4 
Its group number is 2

Answer 2

Very Good question .

Atomic number of element is 20.
Element name is calcium .
Electronic configuration     --------  1s2 2s2 2p6 3s2 3p6 4s2
Number of valence electrons : 2

So,
Element belongs to 4th  period.
 and Group 2