Question

An element 'X' has mass number 35 and number of neutrons 18. Write atomic number and electronic configuration of 'X'. Also write group number, period number and valency of 'X'.

Answer 1

Atomic number of X = Mass number of X - Number of neutrons
=35-18=17
Therefore, electronic configuration of X = 2, 8, 7
Group number = 17
Period number = 3
Valency=8-7=1