Periodic Table – an arrangement of the elements in order of their atomic numbers.
Periodic Law – a natural law that states that the physical and chemical properties of the
elements are periodic functions of their atomic numbers.
Group – a vertical column of the periodic table that contains elements with similar
configurations.
Family – also known as a group.
Period – a horizontal row of elements in the periodic table.
Alkali metal – an element in Group 1a of the periodic table.
Alkaline earth metal – an element in Group 2a of the periodic table.
Halogen – a reactive nonmetallic element in Group 7a of the periodic table.
Noble gas – an inactive element in Group 8a of the periodic table.
Metal – an element that typically has a high melting point, is ductile, malleable, shiny,
and a good conductor of heat and electricity; found on left side of periodic table. a
Nonmetal – an element that has a low melting point and a dull surface, breaks easily, a
poor conductor of heat and electricity and tends to gain electrons in a chemical
reaction.
Semimetal – an element that does not have metallic properties; found on right side of the
periodic table.
Valence electron – an electron in the outermost energy level of an atom; for most atoms,
it’s available to be gained, lost, or shared in the formation of chemical bonds.
Abbreviated electron configuration – shorthand notation describing the distribution of
electrons among the energy levels of an atom.
Noble gas inner core - a group of electrons in an atom’s inner, filled energy levels.
Periodic trend – a property of elements that can be predicted from the arrangement of the
periodic table.
Atomic radius - the distance between the center of the nucleus of an atom and the
outermost electrons.
Ionization energy – the energy required to remove the most loosely held electron from an
atom.
Electron affinity – an energy change that occurs when an atom gains an electron.
Electro negativity – the property of an element that indicates how strongly an atom of
that element attracts electrons in a chemical bond.