Quantum Numbers

Quantum Numbers - Explained

Tip: This isn't the place to ask a question because the teacher can't reply.

Key Questions

Quantum numbers are used to describe the position of an electron in an atom.

Explanation:

Quantum numbers can be used to describe the exact location of an electron.

There are four quantum numbers:

1. n - describes the energy level

2. ℓ - describes the subenergy level (0 to n-1 )

3. mℓ - describes the orbital ( -ℓ to +ℓ )
4. ms - describes the spin (clockwise or anti clockwise : or )

• Quantum numbers refer to electrons, so I'll assume you mean the electron number that would correspond with the atomic number of the element. Quantum numbers are basically like an address for electrons, giving us information about the location of an electron from most general to most specific.

We need to apply the Aufbau principle, Hund's rule and the Pauli exclusion principle to answer this question.

Quantum numbers are listed in the following order: n, l, ${m}_{l}$, ${m}_{s}$

n = principal number - tells us which energy level an electron is in
l = angular number - tells us which sublevel and electron is in
${m}_{l}$ = magnetic number - tells us which orbital the e- is in
${m}_{s}$ = spin number - tells us if the electron is spin up or spin down

The quantum numbers for electron 1 (hydrogen) are: 1,0,0,+1/2
2 (He): 1,0,0,-1/2
3 (Li): 2,0,0,+1/2
4 (Be): 2,0,0,-1/2

There is a lot of info you'll need to understand... - I'll recommend this video to help. Quantum numbers are discussed in the final minute but there is info through the entire video you'll use to determine quantum numbers.

• Zero electrons.
Electrons don't share quantum numbers. Each electron has it's own quantum number. Something similar like people have unique fingerprint. Quantum number "is telling" us everything about electron.

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