Question

An element X has mass no.35 and no.of neutron is 18 .identify the group no. And period of X

Answer 1

Mass number = Atomic number + no. of neutrons
Atomic number = Mass number - no. of neutrons
                         = 35-18 = 17 
Electronic configuration = 2,8,7
Group no- 17
(Valence electrons 7 means group = 10+7 = 17)
Period - 3
(Electronic configuration shows 3 shells means period 3)
 

Answer 2

Answer:

We know :

Atomic number = Mass number - No. of neutrons.

Atomic number = 35 - 18

= > 17

Electronic configuration :

2 , 8 , 7

Group no. = 17

Period no. = 3

Name of element is Chlorine (  Cl ) .