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Atomic Structure & Periodicity

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Atomic Structure & Periodicity

Alkali Metals

The group 1 elements — lithium through francium — which have a single valence s electron.

ns¹ Dimensionless
Atomic Structure & Periodicity

Alkaline Earth Metals

The group 2 elements — beryllium through radium — which have two valence s electrons.

ns² Dimensionless
Atomic Structure & Periodicity

Atomic Emission Spectrum

The pattern of discrete wavelengths emitted when excited atoms of an element return to lower energy states.

ΔE = hν nm
Atomic Structure & Periodicity

Atomic Number

The number of protons in the nucleus of an atom, which uniquely identifies the element.

Z = number of protons Dimensionless
Atomic Structure & Periodicity

Atomic Orbital

A mathematical function describing the region around a nucleus where an electron of given energy is most likely to be found.

|ψ|² = probability density Dimensionless
Atomic Structure & Periodicity

Atomic Radius

A measure of the size of an atom, usually taken as half the distance between the nuclei of two bonded identical atoms.

r = d(X–X) / 2 pm
Atomic Structure & Periodicity

Aufbau Principle

The rule that electrons occupy the lowest-energy orbital available before filling higher-energy ones.

fill in order of increasing (n + l) Dimensionless
Atomic Structure & Periodicity

Azimuthal Quantum Number

The quantum number l that determines the shape of an orbital and the magnitude of the electron's orbital angular momentum.

l = 0 to (n − 1) Dimensionless