Question

the atomic no of an element X is 20 .To which group and period of modern periodic table does X belong . also state its valency

Answer 1

the valency is 2 and the element belongs to the 4th period and the element is calcium.

Answer 2

Answer:

Z = 20

2 , 8 , 8, 2

1 . Since ‘X’ has three energy shells and period number of an element is equal to the number  of energy shells, X belongs to 4rd period.

2 . X has 2 valence electrons it belongs to group 2.

3.  Valency will be 2. To acquire noble gas configuration it will loose 2 electrons.