What are the four quantum numbers in chemistry?

1 Answer
Jun 7, 2018

Answer:

#n#, #l#, #m_l#, and #m_s#.

Explanation:

Electrons can be described by #4# quantum numbers. Here's a brief overview of each of them:

The first quantum number is called the principal quantum number, and it's denoted by the letter #n#. It represents the energy level/shell.

#n# can equal any integer above and including #1#, since #n=1# represents the first principal energy level.

#n = 1,2,3,4...#

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The second quantum number is called the orbital angular momentum number, and it's denoted by the letter #l#.
It represents the number of angular nodes (shown in the first image below) in an orbital, which means that it effectively represents the shape of the orbital.

The maximum value of #l# is #n-1#—the number of angular nodes in an orbital is always one less than the principal energy level.

#l = "0, 1, 2, 3, 4 ... (n-1)"#

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The third quantum number is called the magnetic quantum number, and it's denoted by #m_l#. It describes the orientation of an orbital, which depends on the value of #l#.

#m_l = -l, ..., 0, ..., +l#

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Our fourth quantum number is the electron spin number. It is denoted by #m_s#.

Essentially, every electron has a spin. This a spin is either in the direction of "up" or "down," denoted by the arrows #uparrow# and #downarrow# respectively.

#+1/2# represents #uparrow#, and #-1/2# represents #downarrow#.

#m_s = ±1/2#

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