Chapter 3: Periodic Properties of the Elements

Electron configuration

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

Ground state

The lowest energy state of an atom or molecule.

Orbital diagram

A diagram similar to an electron configuration that 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 stating that no two electrons in an atom can have the same four quantum numbers.

Degenerate

Describes two or more electron orbitals with the same value of n that have the same energy.

Coulomb's law

The law that states that the potential energy (E) of two charged particles depends on their charges (𝑞1 and 𝑞2) and on their separation (r): 𝐸

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 (Zeff)

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 in which some higher-level atomic orbitals have 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

The 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

Noble gases

One of the group 8A elements, which are largely unreactive (inert) due to their stable filled p orbitals.

Metals

A member of a large class of elements that are generally good conductors of heat and electricity, are malleable, ductile, and lustrous, and tend to lose electrons during chemical changes.

Nonmetals

A member of a class of elements that tend to be poor conductors of heat and electricity and usually gain electrons during chemical reactions

Metalloids

A member of a category of elements found on the boundary between the metals and nonmetals of the periodic table, with properties intermediate between those of both groups; metalloids are also called semimetals.

Semiconductors

A material with intermediate electrical conductivity that can be changed and controlled.

Alkali metals

Highly reactive metals in group 1A of the periodic table.

Alkaline earth metals: Fairly reactive metals in group 2A of the periodic table.

Halogens

One of the highly reactive nonmetals in group 7A of the periodic table.

Van der waals radius

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

Covalent raidus

(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

A set of average bonding radii 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.

Ionization 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.