1.
alkali metals: the elements in group 1A of the periodic table, not including hydrogen
2.
alkaline earth metals: metallic elements in group 2 of the periodic table which are harder than the alkali metals and are also less reactive
3.
atomic mass unit: one-twelfth the mass of a carbon-12 atom
4.
group: each column in the periodic table of elements
5.
halogens: an element in group 7A of the periodic table; 7 valence electrons; highly reactive
6.
metalloids: elements with properties that fall between those of metals and nonmetals
7.
metals: elements that are good conductors of electric current and heat
8.
noble gases: elements in group 8A of the periodic table; outer valence shells are full; very stable and nonreactive
9.
nonmetals: elements that are poor conductors of heat and electricity
10.
period: each row in the periodic table of elements
11.
periodic law: when the elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties
12.
periodic table: an arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group
13.
transition metals: elements that form a bridge between the elements on the left and right sides of the table
14.
valence electron: an electron that is found in the outermost shell of an atom and that determines the atom's chemical properties
