Formula of the volatile hydrogen compound of the chemical element H3R. What periodic table is this element on?

Based on the condition, we are interested in a gas that has three hydrogen atoms in its composition. If you look at the periodic table of chemical elements of D.I. Mendeleev, one can understand that not so many gaseous compounds are formed. We are not interested in hydrides, because they are non-volatile compounds.

And from a number of compounds such as silane, phosphine, germane, ammonia, arsine, hydrogen chloride or bromide, hydrogen sulfide, etc. three substances can be noted that fit the desired formula. It:

1) Phosphine PH3,

2) Arsine AsH3,

3) Ammonia NH3.

The last two have a more correct notation: H3As and H3N.