Helium is placed in group 18 on the periodic table because
A.
it has a full outer shell of electrons.
B.
it is highly reactive.
C.
it is a metal.
D.
it has a valence of eight
THE ANSWER IS
it has a full outer shell of electrons.
Answer : A Explanation: The reason of keeping helium in group 18 is that it shows properties similar to noble gases. it is because of its completely filled outer shell which gives it noble gas properties(i.e. it doesnt form compounds,etc).
