The symbol "1" after a compound usually indicates that the compound has one molecule of that particular substance. It's often used in chemical formulas to express the number of moles present in a chemical reaction or equation.

Here are some examples:

* H₂O₁: This would represent one mole of water (H₂O).

* CO₂₁: This would represent one mole of carbon dioxide (CO₂).

Important Note: The "1" is often omitted in chemical formulas because it is understood that a single molecule of the compound is present. So, H₂O₁ is usually just written as H₂O.

However, in some cases, the "1" may be included for clarity or to emphasize that only one molecule is present.