| A | B |
|---|
| periodic table | arrangement of elements in columns, based on a set of properties that repeat from row to row |
| period | Each row in the table of elements |
| group | Each column on the periodic table |
| periodic law | Properties of elements repeat in a predictable way when atomic numbers |
| atomic mass unit | defined as one twelfth the mass of a carbon-12 atom |
| metals | elements that are good conductors of electric current and heat |
| transition metals | elements that form a bridge between the elements on the left and right sides of the table |
| nonmetals | elements that are poor conductors of heat and electric current |
| metalloids | elements with properties that fall between those of metals and nonmetals |
| valence electron | an electron that is in the highest occupied energy level of an atom |
| alkali metals | metals having a single valence electron and are extremely reactive |
| alkaline earth metals | metals having two valence electrons |
| halogens | elements with seven valance electrons all nonmetals |
| noble gases | colorless and odorless and extremely unreactive |
| Antoine Lavoisier | grouped the known elements into categories he called metals, nonmetals, gases, and earths |
| modern periodic table | elements are arranged by increasing atomic number |
| Mendeleev's Periodic Table | elements are arranged by increasing atomic mass |
| periods from left to right | elements become less metallic and more nonmetallic in their properties |
| elements in group have similar properties | because they have the same number of valence electrons |
| alkali metal reactivity | increases from top to bottom of group |
| Group 1 | alkali metals |
| Boron Family | metals having three valence electrons |
| Group 2 | alkaline earth metals |
| Carbon Family | group with four valance electrons, a nonmetal 2 metalloids and 2 metals |
| Group 3 | boron family |
| Group 4 | carbon family |
| Nitrogen Family | group with five valance electrons, 2 nonmetals 2 metalloids and 1 metal |
| Group 5 | Nitrogen Family |
| Oxygen Family | group with six valence electrons 3 nonmetals 2 metalloids |
| Group 6 | Oxygen Family |
| Group 7 | halogens |
| Group 8 | noble gases |
| Dobreiner | identified groups of 3 elements with similar properties |
| Dobriener's Group of 3 Elements | Triad |
| Newlands | properties of elements repeat every 8 elements |
| properties of elements repeat every 8 elements | Law of Octaves |
