Electrons in Atoms

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Electron Configuration Noun

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[uh-lek-tron kon-fig-yuh-rey-shuhn]

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Electron Configuration

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The specific arrangement and distribution of electrons in various orbitals around the nucleus of an atom.

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Example: This diagram shows how electrons are arranged in specific energy levels, called shells, that orbit the central nucleus of an atom.

Front

Electron Shell Noun

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[uh-lek-tron shel]

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Electron Shell

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A principal energy level surrounding an atom's nucleus, which contains electrons with similar energy.

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Example: This diagram shows a model of a Sodium atom. The concentric circles are the electron shells, and the dots on them are the electrons, organized by energy level.

Front

Subshell Noun

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[suhb-shel]

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Subshell

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A subdivision of a principal energy level, designated by letters s, p, d, and f, containing one or more orbitals.

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Example: Subshells are subdivisions of an electron shell. This image shows the three parts of a 'p' subshell, which are dumbbell-shaped regions where electrons are found.

Front

Orbital Noun

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[awr-bi-tl]

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Orbital

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A specific region within a subshell that can hold a maximum of two electrons with opposite spins.

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Example: This image shows the dumbbell shapes of the three different p-orbitals (px, py, pz), which are regions around an atom's nucleus where an electron is likely to be found.

Front

Electron Spin Noun

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[uh-lek-tron spin]

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Electron Spin

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A quantum mechanical property of an electron, described as either spin-up or spin-down, creating a magnetic field.

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Example: This image shows that an electron's spin creates a tiny magnetic field. The two possible spin directions, 'spin up' and 'spin down', produce opposite magnetic poles.

Front

Aufbau Principle Noun

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[ouf-bou prin-suh-puhl]

Back

Aufbau Principle

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

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Example: This diagram shows the order for filling electron subshells in an atom, starting from the lowest energy level (1s) and following the path of the arrows.

Front

Pauli Exclusion Principle Noun

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

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Pauli Exclusion Principle

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The quantum mechanical principle stating that an atomic orbital can hold a maximum of two electrons with opposite spins.

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Example: This diagram shows that when two electrons occupy the same orbital (the box), they must have opposite spins (one arrow up, one arrow down).

Front

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 that for an atom like Nitrogen, electrons fill empty orbitals of the same energy one at a time before pairing up.

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Valence Electrons Noun

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[vey-luhns uh-lek-trons]

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Valence Electrons

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The electrons located in the outermost shell of an atom, which are involved in forming chemical bonds.

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Example: This diagram of an oxygen atom shows the 6 electrons in the outermost shell. These electrons in the outer shell are the atom's valence electrons.

Front

Core Electrons Noun

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[kawr uh-lek-trons]

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Core Electrons

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The inner-shell electrons of an atom that are not valence electrons and do not participate in chemical bonding.

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Example: This diagram shows an atom model where the inner electrons, called core electrons, are pointed out, distinguishing them from the valence electron on the outermost shell.