Question

What are the four quantum numbers in chemistry?

Answer 1

`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...`

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)"`

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`

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`