does fire have atoms or molecules
Fire is a bunch of atoms. In a flame we find nitrogen, carbon, oxygen and hydrogen atoms. As it glows and produce heat we call it fire.
Fire occurs when a fuel such as gas, wood or paper is put in contact with oxygen at a high enough temperature. When this happens, oxygen atoms (mostly from the air) and carbon atoms (from the fuel) are able to break down and bond together to form molecules such as CO2. By doing so, they release energy in the form of heat, and light that you can see.