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Electron configuration (new)

I. Quantum numbers:
Define the size, shape, orientation, and spin of electrons

II. Each electron has their own unique 4 quantum numbers represented by n, l, m, and s. This is known as the Pauli Exclusion

Sometimes these quantum numbers are represented as n, l, ml, and ms, but here we will just use n, l, m, and s. The n is called the principle quantum number. It’s often referred to as the shell number because in Bohr’s atom, each increasing orbit forms a shell around the inner ones. In the past these shells were called K, L, M, N, and O. Those correspond to n=1, 2, 3, 4, & 5. You may still see reference to these letters in the literature.

Using boxes with electron configuration:
electron confguration of neon

There are 3 names for the l quantum number: azimuthal, angular, and orbital.

…The different orientations are indicated with the m quantum number. This is also called the magnetic quantum number. Notice the m quantum number starts with the negative of the l quantum number. Since we are at the l=1 quantum number (p orbital), the m quantum numbers start out as -1, then go up to 0 on the next electron, and +1 on the third electron…

Practice Problem 8: How many electrons are in this element that has this electron configuration? 1s22s22p3


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