| A | B |
|---|
| atom | smallest particle that makes up all matter |
| atomic number | number of protons in an atom |
| average atomic mass | average mass of an element; weighted average of an element's various isotopes |
| charge | not electrically neutral; having a positive or negative electrical value |
| compound | substance made up of the combined atoms of two or more different elements |
| electrons | negatively charged particles located outside an atom's nucleus |
| electron cloud | region surrounding the nucleus where the electrons are most likely to be found |
| element | substance in which all the atoms in the sample have the same number of protons |
| group | vertical column on the periodic table; made up of elements with similar properties |
| ion | an atom that has lost or gained electrons and now has either a positive or negative charge |
| mass number | sum of the protons and neutrons in the nucleus of an atom |
| metal | elements to the left of the stairstep on the periodic table; shiny, good conductors |
| neutral | having no charge |
| neutron | neutrally charged particle in the nucleus of an atom |
| nonmetal | elements to the right of the stairstep on the periodic table; poor conductors; gases, liquids, or brittle solids |
| nucleus | positively charged core of an atom; contains the protons and neutrons |
| oxidation number | specific positive or negative number that shows an element's tendency to lose or gain electrons when bonding with other atoms |
| period | horizontal rows of the periodic table |
| periodic table | arrangement of the known elements from smallest to largest atomic number; used to identify properties, patterns, and trends among the elements |
| proton | positively charged particle in an atom's nucleus; number of protons gives an atom its identity and its atomic number |
