| A | B |
|---|
| nucleus | the center of an atom |
| proton | a subatomic particle with a positive charge |
| neutron | a subatomic particle with no charge |
| electron | a subatomic particle with a negative charge |
| element | a substance made up of only one kind of atom |
| atom | the smallest unit of an element that has all the properties of that element |
| molecule | two or more atoms linked together |
| periodic table | a chart on which elements are arranged in order of atomic number |
| compound | a substance made of the atoms of two or more elements |
