Question

with atomic number 18 what is the name of element b)to which group it belong to c)to which period it belongs to d)what is the valency

Answer 1

element argon has atomic no. 18
It belongs to 18 group
It is a noble gas
It has 8 electrons in its valence shell

Answer 2

Atomic no. is 18 
the element is Argon
It belongs to 18th group 
It belongs to 3rd period
Argon has a valency of 0.It is because of the reason that electronic configuration of Ar is 2, 8, 8. Since the last shell is filled and its octet is complete so it neither gains nor loose electron.So the valency of Ar is 0.