I think that it is chemical formula.
It is an expression.
Chemical compound
Chemical formulas consist of chemical symbols and numbers. The symbols represent the elements in the compound. The numbers indicate the quantity of atoms of each element in the compound.
A combination of chemical symbols that show what elements make up a compound and the number of atoms of each element in the smallest unit of the compound is a chemical formula.
Subscript
Compounds can be described using element symbols and numbers
Chemical formula
numbers have symbols so you can see how they look
Well, no chemical can actually represent a substance with chemical symbols, but I think you're talking about a chemical formula.
That would depend on what that compound is/is made from.
No. The multiple symbols interrupted by the numbers make it clear that this is a compound. In this case it is copper sulfate, a compound of three elements: copper (Cu), sulfur (S), and oxygen (O).
Yes, hieroglyphics included symbols for numbers.