Periodic table
Arrangement of the elements in order of their atomic numbers so that elements with similar electron configuration are located in the same column.
Periodic law
Natural law that states that the physical and chemical properties of the elements are periodic functions of their atomic numbers.
group
Vertical column of the periodic table that contains elements with similar electron configurations. Also called families.
family
Vertical column of the periodic table that contains elements with similar electron configurations. Also called groups.
period
Horizontal row of elements in the periodic table.
alkali metal
Element in Group 1A of the periodic table.
alkaline earth metal
Element in Group 2A of the periodic table.
halogen
Reactive, nonmetallic element in Group 7A of the periodic table.
noble gas
Inactive element in Group 8A of the periodic table.
metal
Element that typically has a high melting point, is ductile, malleable, shiny and a good conductor of heat.
nonmetal
Element that has a low melting point and a dull surface, breaks easily, is a poor conductor of heat and electricity, and tends to gain electrons in a chemical reaction.
semimetal
Element that does not have metallic properties, found on the right side of the periodic table. Also called metalloids.
valence electron
Electron in the outermost energy level of an atom; for most atoms, it is available to be gained, lost or shared in the formation of chemical bonds.
abbreviated electron configuration
Shorthand notation using the preceding noble gas to describe the distribution of electrons among the energy levels of an atom.
noble gas inner core
Group of electrons in a atom's inner filled energy levels; configured much like electrons in a noble gas.
periodic trend
Property of the elements that can be predicted from the arrangement of the periodic table.
atomic radius
Distance between the center of the nucleus and the outermost electrons.
ionization energy
Energy required to remove the most loosely held electron from an atom.
electron affinity
Energy change that occurs when at atom gains an electron.
electronegativity
Property of an element that indicates how strongly an atom of that element attracts electron in a chemical bond.
ductile
Able to be drawn out into a thin wire.
malleable
Able to be hammered or pressed permanently out of shape without breaking or cracking.