Electron Configurations and Orbital Diagrams

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Electronic Configuration Noun

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[eh-lek-tron-ik kon-fig-yuh-rey-shuhn]

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Electronic Configuration

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The specific arrangement and distribution of electrons within the orbitals of an atom or molecule.

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Example: This Bohr model shows the electronic configuration of a Sodium (Na) atom, with 2 electrons in the first shell, 8 in the second, and 1 in the third.

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Orbital Noun

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[awr-bi-tl]

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Orbital

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A three-dimensional region around an atom's nucleus where there is a high probability of finding an electron.

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Example: This diagram shows the three p-orbitals (px, py, pz), which are dumbbell-shaped regions where an electron can be found, each aligned along a different axis.

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Quantum Numbers Noun

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[kwon-tuhm nuhm-berz]

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Quantum Numbers

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A set of four numbers used to describe the unique energy state and location of an electron in an atom.

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Example: This diagram shows the different shapes of atomic orbitals (s, p, d, f), which are regions in space where an electron is likely to be found.

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Principal Quantum Number (n) Noun

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[prin-suh-puhl kwon-tuhm nuhm-ber]

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Principal Quantum Number (n)

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The quantum number indicating the main energy level or shell an electron occupies, which relates to its size and energy.

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Example: This diagram shows an atom's electron shells, which are the main energy levels. The principal quantum number (n) is used to label these shells.

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Orbital Angular Momentum Quantum Number (l) Noun

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[awr-bi-tl ang-gyuh-ler moh-men-tuhm kwon-tuhm nuhm-ber]

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Orbital Angular Momentum Quantum Number (l)

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The quantum number that describes the shape of an atomic orbital and designates its sublevel (s, p, d, or f).

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Example: This chart shows that the orbital angular momentum quantum number (l) determines the shape of an electron orbital: l=0 is a spherical 's' orbital, l=1 is a dumbbell 'p' orbital, etc.

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Magnetic Quantum Number (ml) Noun

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[mag-net-ik kwon-tuhm nuhm-ber]

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Magnetic Quantum Number (ml)

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The quantum number specifying the orientation of an orbital in three-dimensional space relative to the other orbitals.

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Example: This table shows the relationship between the principal quantum number (n) and the angular momentum quantum number (l), but it does not illustrate the magnetic quantum number (ml).

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Electron Spin Quantum Number (ms) Noun

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[eh-lek-tron spin kwon-tuhm nuhm-ber]

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Electron Spin Quantum Number (ms)

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The quantum number describing the intrinsic angular momentum of an electron, which has two possible spin directions.

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Example: This diagram shows that an electron can have two spin states, "spin up" (ms = +1/2) or "spin down" (ms = -1/2), which are represented by opposing arrows in an orbital.

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Aufbau Principle Noun

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[ouf-bou prin-suh-puhl]

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Aufbau Principle

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The rule stating that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels.

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Example: This diagram uses arrows to show the correct order for filling electron orbitals in an atom, starting from the lowest energy level (1s) and moving up.

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Pauli Exclusion Principle Noun

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[paw-lee ik-skloo-zhuhn prin-suh-puhl]

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Pauli Exclusion Principle

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

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Example: This image shows that two electrons in the same orbital (box) must have opposite spins (one up arrow, one down arrow), which is the Pauli Exclusion Principle.

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Hund's Rule Noun

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[hundz rool]

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Hund's Rule

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The rule that every orbital in a subshell is singly occupied before any orbital is doubly occupied.

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Example: This diagram shows how electrons fill separate orbitals (boxes) with the same spin (up arrows) before pairing up, as seen from Carbon to Nitrogen.