| A | B |
|---|
| element | a pure substance that cannot be broken down into any simpler substances |
| compound | any substance that is formed by the chemical combination of two or more elements and acts like a single substance |
| pure substances | a large class of matter made up of elements and compounds |
| atom | the smallest unit of an element that retains the properties of that element |
| nucleus | an atom’s dense center, where most of its mass is |
| proton | a particle in the nucleus of an atom that carries one unit of positive electric charge |
| electron | a particle in the space outside the nucleus of an atom that carries one unit of negative electric charge |
| neutron | a particle in the nucleus of an atom that has no net electric charge |
| molecule | a particle that contains more than one atom joined together |
| nucleus |  |
| proton |  |
| electron |  |
| neutron |  |
