Answer:
Period no. = 1, Group no. = 18
Step-by-step explanation:
Atomic number of He = 2
Helium is placed in period 1 and group 18.
Helium is an inert gas and also known noble gas.
Helium is the first element placed in group 18.
Helium is a colourless, odder-less gas. Its outer shell (K shell) is fully occupied and so has inert gas configuration.
Because of inter gas configuration, it is chemically inactive.