## Quantum numbers

IreneSeo3F
Posts: 57
Joined: Wed Sep 30, 2020 9:31 pm

### Quantum numbers

Hi!! While I was doing the sapling questions, I was just wondering if we have to memorize the quantum numbers for every subshell or there is a particular way to calculate/figure them out?

Sam Wentzel 1F 14B
Posts: 80
Joined: Wed Sep 30, 2020 9:50 pm
Been upvoted: 1 time

### Re: Quantum numbers

"n" correlates to the leading number of the subshell, and represents the main shell that an electron occupies.

For example, in "3s2," n = 3 because of the leading "3" before the "s2".

l correlates to the subshell of the electron. l = 0 correlates to the s subshell, l = 1 to the p subshell, l = 2 to the d, and l = 3 to the f.

The l value of 3s2 would be 0, as it is in the s subshell.

ml defines the sub-orbital that the specified electron occupies. If we are specifying the last electron in say, 3p6, then ml would be equal to 1.
The way you determine ml, is the middle pair of electrons is always at ml = 0. The pair of electrons before that will be at ml = -1, -2, and so on.
The pair of electrons after the middle pair will always be positive, at ml = 1, 2, and so on.

The quantum number ms corresponds to which electron in an electron pair is being specified. The "first" electron in each electron pair will always have upward spin, with an ms value of ms = +1/2. The second electron in each electron pair will always have an ms value of -1/2, with a downward spin.

The only real thing to memorize is what each quantum number correlates to in terms of electron configuration. After knowing this, one can determine the quantum numbers of a specified electron / element simply by using logical application of what each quantum variable corresponds to.

Hope this helps :)

AlyssaMaynard1C
Posts: 60
Joined: Fri Mar 06, 2020 12:15 am

### Re: Quantum numbers

IreneSeo3F wrote:Hi!! While I was doing the sapling questions, I was just wondering if we have to memorize the quantum numbers for every subshell or there is a particular way to calculate/figure them out?

I'm also confused on this because I try to look for patterns and know which sub shell has which number, but when questions ask about ml it makes me question my thought.