In atomic physics and quantum chemistry, the electron configuration is the arrangement of electrons in an atom, molecule or other body. Specifically, it is the placement of electrons into atomic, molecular, or other forms of electron orbitals. The electrons occupy specific probability regions, whose shapes and electron capacity are denoted by the letters s,p,d,f and the as of yet unseen g,h, and i. The energy of an orbital is shown by a whole number (1-7) next to the letter, electrons are able to jump from one energy level (orbital filling laws allowing) to another by emission of a quantum of energy, in the form of a photon

Electron configuration in atoms

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The discussion below presumes knowledge of material contained at Atomic orbital.

Summary of the quantum numbers

The state of an electron in an atom is given by four quantum numbers. Three of these are integers and are properties of the atomic orbital in which it sits (a more thorough explanation is given in that article).

number	denoted	allowed range	represents
principal quantum number	n	integer, 1 or more	partly the overall energy of the orbital, and by extension its general distance from the nucleus
azimuthal quantum number	l	integer, 0 to n-1	the orbital's angular momentum, also seen as the number of nodes in the density plot
magnetic quantum number	m	integer, -l to +l	determines energy shift of an atomic orbital due to external magnetic field (Zeeman effect).
spin quantum number	s	+½ or -½ (sometimes called "up" and "down")	Spin is an intrinsic property of the electron and independent of the other numbers. s and l in part determine the electron's magnetic dipole moment.

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