How can you find the relative formula mass of a compound?

To find the relative formula mass of a compound, you need to add the relative atomic masses of all the atoms present in the compound. Each element has a specific relative atomic mass, typically found on the periodic table, and the formula mass is calculated by summing these values, taking into account how many of each type of atom are in the compound.

For example, in water (H₂O), you would take the relative atomic mass of hydrogen (approximately 1) and multiply it by 2 for the two hydrogen atoms, then add it to the relative atomic mass of oxygen (approximately 16). This gives you a total relative formula mass of 18 for water.

The other options do not accurately describe the method for calculating the relative formula mass and may lead to misunderstandings. Therefore, summing the relative atomic masses of all the atoms is the correct approach.