Some molecules are always found in pairs These are called __ molecules. How many atoms of each kind are there? __ Write in the name of the molecule in the blank.

## Step 1<br />The problem is asking for the name of a type of molecule that is always found in pairs. This is a characteristic of diatomic molecules.<br /><br />## Step 2<br />Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements. The prefix "di-" is of Greek origin, meaning "two". If a diatomic molecule consists of two atoms of the same element, such as hydrogen (H2) or oxygen (O2), then it is said to be homonuclear. Otherwise, if a diatomic molecule consists of two different atoms, such as carbon monoxide (CO) or nitric oxide (NO), the molecule is said to be heteronuclear.<br /><br />## Step 3<br />The number of atoms of each kind in a molecule is determined by the molecular formula. For example, in the molecule H2, there are two hydrogen atoms. In the molecule CO, there is one carbon atom and one oxygen atom.