Make up the formulas of hydrogen compounds of the following elements: S (II), P (III), F (I), C (IV).

Explanation of the solution to the problem: the valency of an element in a given compound is indicated in brackets, which can have several valency values, depending on which element it forms a chemical bond with.
a) Н2S – hydrosulphuric acid (valency Н is always equal to 1; S – 2);
b) PH3 – phosphine (valence H – 1; P – 3);
c) HF – hydrofluoric (hydrofluoric) acid (valence H – 1; F – 1);
d) CH4 – methane (valence H – 1; C – 4).