This is a parody of a song, and is meant to go with this tune. You can use this to remember which prefix goes with which number when you talk about a compounds.

Simple chemistry my dear. One of an element is mono-.

Simple chemistry my dear. Two of an element is di-.

Simple chemistry my dear. Three of an element is tri-.

Simple chemistry my dear. Four of an element is tetra-.

Simple chemistry my dear. Five of an element is penta-.

Simple chemistry my dear. Six of an element is hexa-.

Simple chemistry my dear. Seven of an element is hepta-.

Simple chemistry my dear. Eight of an element is octa-.

Simple chemistry my dear. Nine of an element is nona-.

Simple chemistry my dear. Ten of an element is deca-.