Having designated a chemical element by the symbol R, write in general form the formulas

Having designated a chemical element by the symbol R, write in general form the formulas of hydrogen compounds: a) halogens; b) chalcogenes.

Halogens are elements that are in the main subgroup of the seventh group of the periodic table.
These are fluorine, chlorine, bromine, iodine and astatine. Their name in translation means salt-forming, since they are found in the composition of salts. The most famous salt is sodium chloride, which we add to food. The formula for a hydrogen compound is RH.
Chalcogenes, which means giving birth to copper, are elements of the oxygen subgroup: O, S, Se, Te. The formula for their hydrogen compound is H2R. In nature, they often combine with copper.