1st period has ………shells.
a) one
b) two
c) three
d) four
Hydrogen (H) and Helium (He) lies in.…… period.
a) 4th
b) 3rd
c) 1st
d) 5th
Hydrogen (H) and Helium (He) lies in.…… period.
a) 4th
b) 3rd
c) 1st
d) 5th
1st period is also called…………period.
a) shortest
b) long
c) short
d) very long
Lithium is present by the……. period.
a) 4th
b) 3rd
c) 2nd
d) 5th
2nd & 3rd periods contain……elements each.
a) eight
b) eighteen
c) two
d) ten
