Consider the following unbalanced particulate representation of a chemical equation: H = light blue
I = purple
Write a balanced chemical equation for this reaction, using the smallest integer coefficients possible. Do not include states.

H2 + I2 --> 2HI

Explanation:

The two reactants are diatomic molecules because they contain two atoms of the same element. Therefore, they would need to have a subscript of "2" next to their symbols.

When balancing an equation, you want the same amount and type of atoms on both sides. By adding a coefficient of "2" in front of the product, two H's and two I's are now on both sides.