Final answer:
A shorthand notation of a substance composition using atomic symbols and numerical subscripts is called a chemical formula, with molecular formulas indicating the exact number of atoms of each type in a molecule.
Step-by-step explanation:
A shorthand representation of the composition of a substance using atomic symbols and numerical subscripts is called a chemical formula. A molecular formula is a specific type of chemical formula that uses atomic symbols accompanied by subscripts that indicate the number of atoms of each element in the molecule—only present when the atom count is greater than one. This notation is crucial in conveying information about the proportion and types of atoms that constitute a particular compound.
The molecular formula, while displaying the actual number of each type of atom, does not illustrate the arrangement of atoms or the bonds between them, which is depicted by other types of formulas like the structural formula. Chemical formulas are essential in chemistry as they serve as the language that describes the composition of compounds succinctly and effectively.