Scientific Tutor

What are diatomic molecules?

Before we go forward to predicting chemical equations we need to completely explain one concept. That concept is diatomic molecules. First a definition. The word diatomic breaks down into two parts DI- meaning 2 and –ATOMIC meaning atom. So it is molecule made up of two atoms. More specifically it is a molecule made up of two atoms from the same element. These diatomic molecules form because of their abundance in the chemical equation, their stability as a molecule, and their valence electron sharing.  You can predict their existence through Valence Electron Dot Structures (Lewis Structures).

The diatomic elements are:

H / N / O / F / Cl / Br / I

They form the diatomic molecules:

H₂ / N₂ / O₂ / F₂ / Cl₂ / Br₂ / I₂

How do I memorize these diatomic molecules?

Two ways I have found that help you memorize the diatomic molecules are:

1)  Use a mnemonic, a word or words that reminds you of a thing or concept you want to remember.  For diatomic molecules people use the mnemonic  BrINClHOF.  It sounds like Brinkelhoff.

2)  Look at the pattern on the periodic table like the picture below.

What is important about diatomic molecules for predicting chemical equations?

When you predict the products of a chemical equation often times it will contain diatomic molecules. What you want to get familiar with in this section is spotting elements that will form those diatomic molecules.

Examples: Identify which elements form diatomic molecules and then write their diatomic molecules. If they do not form diatomic molecules then write NOT.

PRACTICE PROBLEMS: Identify which elements form diatomic molecules and then write their diatomic molecules. If they do not form diatomic molecules then write NOT.