2. The Ties that Bind

Let’s do a little chemistry. Say we have some hydrogen gas, some chlorine gas, a tiny spark, and a big insurance policy. We can create hydrogen chloride and a most impressive explosion. Chemists write the reaction thus:

H₂ + Cl₂ ----> 2 HCl

Okay, what does all that mean? H₂ is the symbol for a molecule of hydrogen gas, which exists as two atoms of hydrogen bound to each other. Cl₂ is the symbol for a molecule of chlorine gas, which exists as two atoms of chlorine bound to each other. And 2 HCl means "two molecules of HCl." A molecule of HCl, as you’ve probably deduced, is an atom of hydrogen bonded to an atom of chlorine. So this equation tells us that if we combine hydrogen gas and chlorine gas, we get hydrogen chloride gas.

But it doesn’t tell us how it happens. Let’s go back to the Bohr model.