Chapter 9: Periodic Properties of the Elements

Periodic property

A property of an element that is predictable based on an element's position in the periodic table.

Electron configuration

A notation that shows the particular orbitals that are occupied by electrons in an atom.

Ground state

The lowest energy state in an atom, ion, or molecule.

Orbital diagram

A diagram that gives information similar to an electron configuration but symbolizes an electron as an arrow in a box representing an orbital, with the arrow's direction denoting the electron's spin.

Pauli exclusion principle

The principle that no two electrons in an atom can have the same four numbers.

Degenerate

A term describing two or more electron orbitals with the same value of n that have the same energy.

Coulomb's law

A scientific law stating that the potential energy between two charged particles is proportional to the product of the charges divided by the distance that separates the charges.

Shielding

The effect on an electron of repulsion by electrons in lower-energy orbitals that screen it from the full effects of nuclear charge.

Effective nuclear charge

(Z_eff) The actual nuclear charge experienced by an electron, defined as the charge of the nucleus plus the charge of the shielding electrons.

Penetration

The phenomenon of some higher-level atomic orbitals having significant amounts of probability within the space occupied by orbitals of lower energy level. For example, the 2s orbital penetrates into the 1s orbital.

Aufbau principle

The principle that indicates the pattern of orbital filling in an atom.

Hund's rule

The principle stating that when electrons fill degenerate orbitals, they first fill them singly with parallel spins.

Valence electrons

Those electrons that are important in chemical bonding. For main-group elements, the valence electrons are those in the outermost principal energy level.

Core electrons

Those electrons in a complete principal energy level and those in complete d and f sublevels.

Van der Waals radius

(nonbonding atomic radius) One-half the distance between the centers of adjacent, nonbonding atoms in a crystal.

Covalent radius

(bonding atomic radius) In nonmetals, one-half the distance between two atoms bonded together, and in metals one-half the distance between two adjacent atoms in a crystal of the metal.

Atomic radius

The average bonding radius of an atom determined from measurements on a large number of elements and compounds.

Paramagnetic

The state of an atom or ion that contains unpaired electrons and is, therefore, attracted by an external magnetic field.

Diamagnetic

The state of an atom or ion that contains only paired electrons and is, therefore, slightly repelled by an external magnetic field.

lonization energy

(IE) The energy required to remove an electron from an atom or ion in its gaseous state.

Electron affinity

(EA) The energy change associated with the gaining of an electron by an atom in its gaseous state.