Final answer:
To write the formula for a molecular compound, determine the number of atoms of each element present in the compound. Use numerical prefixes to indicate the number of atoms of each element.
Step-by-step explanation:
To write the formula for a molecular compound, you need to determine the number of atoms of each element present in the compound. The element that appears first in the compound formula is usually the one closest to the left side of the periodic table. The second element is named by adding the suffix -ide to the stem of the element name. Use numerical prefixes to indicate the number of atoms of each element, as shown in the Table below:
For example, if you want to write the formula for carbon dioxide, you would start with the element carbon, which is closer to the left side of the periodic table. The element oxygen, which is closer to the right side, gets the -ide suffix. Since there is one atom of carbon and two atoms of oxygen in each molecule, the formula for carbon dioxide is CO2.