Question

An element X has the mass number 40 and the number of neutron is 20 to identify the group number and period of x

Answer 1

Mass number=No.of neutrons(n)+No.of protons(p)
40=20+p⇒p=40-20=20
∴Atomic Number=No.of protons=20
Electronic configuration of X=2,8,8,2
Since the outermost shell of X has 2 electrons.
∴Valency of X=2

Answer 2

electronic confrigation of element X is 2,8,8,2
this means 2nd group and 4period
no.of shell=period
and valancy =group