| A | B |
|---|
| Nucleus | central part of two particles |
| Protons | positively charged particles |
| Electrons | negatively charged particles |
| Neutrons | neutral; no charge |
| Electron cloud | outer layers of orbiting electrons |
| Periodic table | Chart of elements listed in increasing atomic number |
| Periods | horizontal rows; all have different properties |
| Groups or Families | vertical rows; have similar properties because they have the same number of electrons in their outer shells |
| Atomic number | number of protons |
| Atomic mass | protons +neutrons |
| Chemical symbol | short abbreviation for the element |
| Chemical formula | shows the elements and number of each in a compound |
| Subscripts | tell the number of atoms of that element |
| Chemical equation | shows the reactants and products of a chemical reaction |
| Coefficients | number in front of the chemical or formula |
| Element | pure substance that cannot be broken down further by ordinary chemical means |
| Compound | Two or more elements that have been chemically combined and can be broken down by ordinary chemical means |
| Mixture | solutions that are not chemically bonded together so that each retains its own distinctive properties |
