The valency of neon is

The valency of hydrogen is 1, magnesium, 2 aluminium 3 and carbon 4 . Can you see any connection between the valency of an element and the number of electrons it has in its outermost electron shell ? What would you predict the valencies of helium (He), phosphorus (P), sulphur (S) and neon (Ne) to be ?

The density of neon gas will be highest at

The density of neon will be highest at :