What is the simplest whole-number ratio of atoms in a molecule or formula unit called?

Hi there! The simplest whole-number ratio of the atoms in a molecule of formula is called the Empirical formula.

Answer: Empirical formula

Empirical formula referst to the simplest whole-number ration of atoms in a molecule. A compound's molecular formula can either be the same or multiple of its empirical formula. The structural and molecular formulas are also part of the compound formulas