| A | B |
|---|
| Mendeleev's Periodic Table | elements arranged in the periodic table in order of increasing atomic mass |
| Modern Periodic Table | elements are arranged in order of increasing atomic number |
| Metals | good conductors of heat and electricity |
| ductile | can be drawn into wire |
| malleable | can be pounded into thin sheets |
| nonmetals | mostly gases at room temperature |
| metalloids | have properties of both metals and nonmetals |
| alkali metals | group 1A elements |
| alkaline earth metals | group 2A elements |
| halogens | group 7A elements |
| noble gases | group 8A elements |
| representative elements | group A elements (s and p sublevels) |
| transition elements | group B elements in the d sublevels |
| inner transition elements | elements in the f sublevels |
| atomic radius | one half the distance between the nuclei of two atoms of the same element when the atoms are joined |
| ion | an atom or group of atoms that has a positive or negative charge |
| cation | an ion with a positive charge |
| anion | an ion with a negative charge |
| ionization energy | energy required to remove an electron from an atom |
| electronegativity | the ability of an atom of an element to attract electrons when the atom is in a compound |
