The Basics of Atomic Bombs

Do you know how atomic bombs work? Oh, God. In the basics. So they basically create a chain reaction where they have something decays and releases a neutron which then splits into another atom. The number of protons tell you what element it is but that doesn't determine the number of neutrons. You could have oxygen with as many neutrons as you want. And it's still going to be the oxygen still will be that element.