Organic Chemistry: Atomic Structure

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Terms

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Terms

Anion

An ion with a net negative charge.
Atomic orbital

An orbital that is associated with only one particular atom. This is in contrast to molecular orbitals, which are spread across a collection of atoms.
Aufbau principle

German for "building up", a systematic procedure for determining the electron configuration of any atom.
Cation

An ion with a net positive charge.
Degenerate orbitals

Orbitals with identical energies.
Electron affinity

The energy change in an atom when it gains an electron.
First ionization energy

The energy cost of removing one electron from an atom.
Hund's Rule

A rule which says that electrons prefer to go in separate orbitals when choosing between orbitals of the same energy, in order to half-fill orbitals.
Ion

Any atom or molecule with a net charge.
Ionic bond

Bonding interaction that results from electrostatic attraction between cations and anions.
Ionization energy

The energy it takes to remove an electron from an atom.
Isoelectronic

Description for two elemental species with the same electronic configuration.
Isotope

Atoms with the same number of protons (i.e. same atomic number) but a different number of neutrons.
Octet rule

The cardinal rule of bonding. The octet rule states that atoms gain stability when they have a full complement of 8 electrons in their valence shells.
Orbital

The region around an atom where an electron has a high probability of being found.
Pauli Exclusion Principle

States that no two electrons in an atom or molecule can have the same set of four quantum numbers n, l, m, and s.
Second ionization energy

The energy cost of removing a second electron from an atom.
Shell

A group of subshells of similar energy levels. 2s and 2p subshells occupy the same shell.
Shielding

When the attraction from the nucleus felt by one electron is lessened or blocked by intermediate electrons. Shielding can split degenerate orbitals. For example, since s-orbital electrons shield for p-orbital electrons and receive little shielding themselves, s-orbitals are usually of lower energy level than p-orbitals of the same shell.
Splitting

The breaking of degenerate orbitals within a shell in multi-electron atoms.
Subshell

Orbitals in an atom with the same energy; orbitals of the same subshell are of the same shape. p-orbitals are of the same subshell, while s-orbitals are of a separate subshell.
Uncertainty Principle

A tenet of quantum mechanics which says that the position and momentum of any particle cannot both be known precisely at the same time.
Valence electron

The electrons in the outermost energy shell of an atom. The configuration of these electrons determine the chemical properties of the element.
Valence shell

The highest energy shell in an atom. All interactions between atoms take place through the electrons of the valence shell.

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