AP Chem Unit 3: The Periodic Table

electronegativity

a qualitative chemical property that describes the ability of an atom to attract electrons toward itself, measured from Pauling units. Elements on the top right of the periodic table (excluding the noble gases) have the highest electronegativity.

electron affinity

a quantitative amount of energy (usually in kJ/mol) released when a neutral atom or molecule gains an electron from an exterior source, like electronegativity. Elements on the top right of the periodic table (excluding the noble gases) have the highest electron affinities.

first ionization energy

the energy needed to remove the outermost (highest energy) electron from a neutral atom. Elements on the top right of the periodic table (including the noble gases) have the highest first ionization energy; elements on the lower left have the lowest first ionization energies.

atomic radius

the distance from the center of the nucleus of an atom to the boundary of the surrounding levels of electrons. Elements on the bottom left have the highest atomic radii because within a row, the same electron shell is being filled, but the nucleus's charge goes up.

effective nuclear charge

the net positive charge experience by an atom's valence electrons, taking into account the shielding effect of inner electrons. There is an increase as you move down a column because within a group, more electron levels are added as you move down.

ionic radius

the distance from the center of the nucleus to the boundary of the surrounding shells of electrons of an ion. Anions will have larger radii than their parent atoms, whereas cations will have smaller radii than their parent atoms.

metal

an element that is shiny, usually solid at room temperature, malleable, and a good conductor of heat and electricity. Al, Ga, In, Sn, Tl, Pb, and Bi are considered metals.

alkali metal

a group 1 element (except for hydrogen).

alkaline earth metal

a group 2 element.

transition metal

a group 3–12 element.

nonmetal

an element that is generally a gas or a brittle, dull-looking solid. Nonmetals can be found on the right side of the bold line in the periodic table.

halogen

a nonmetal and highly reactive element in group 17.

noble gas

an unreactive gas in group 18.

metalloid

an element that has physical and chemical properties of both metals and nonmetals. The metalloid elements are B, Si, Ge, As, Sb, and Te.

ionic bonding

bonding that involves a complete transfer of electrons, usually existing between a positively charged metal/polyatomic ion and a negatively charged nonmetal/polyatomic ion.

covalent bonding

bonding that involves sharing of electrons through the formation of covalent bonds, usually existing between nonmetals/metalloids. Covalent bonds also hold polyatomic ions together.

metallic bonding

bonding that exists between metal atoms in elemental metals and alloys and can be described as a "sea of electrons" freely surrounding positively charged metal nuclei.

polyatomic ion

an ion made up of more than one atom that can act as an ion in an ionic compound.