Question

Question #9b3cf

Answer 1

Here's what I got.

Explanation:

The first thing to do here is to write the electron configuration of a neutral aluminium atom.

Aluminium is located in period 3, group 13 of the Periodic Table of Elements and has a total of `13` electrons surrounding its nucleus, as given by its atomic number.

The electron configuration of a neutral aluminium atom looks like this

`"Al: " 1s^2 2s^2 2p^6 3s^2 color(blue)(3)p^1`

As you can see, the last electron present in an aluminium atom is located in a `3p` orbital.

Now, we need to find the values of the four quantum numbers used to describe the position and spin of an electron inside an atom.

In your case, the principal quantum number, `n`, which gives the energy level on which the electron is located, is equal to `color(blue)(3)`.

The angular momentum quantum number, `l`, which gives you the subshell in which the electron is located, is equal to `1`, since

• `l=0 ->` designates the s subshell
• `l=1 ->` designates the p subshell
• `l=2 ->` designates the d subshell

and so on. The magnetic quantum number, `m_l`, which gives you the orbital which holds the electron, can take one of three possible values here

• `m_l = -1 ->` the `3p_x` orbital
• `m_l = color(white)(-)0->` the `3p_z` orbital
• `m_l = color(white)(-)1 ->` the `3p_y` orbital

Because in the case of an aluminium atom the p subshell contains a single electron, you can pretty much pick any of these three values for `m_l`.

Let's say that we have `m_l = 0` for an electron located in the `3p_z` orbital.

Finally, the spin quantum number, `m_s`, which tells you the spin of the electron, can be `+1/2` for an electron that has spin-up and `-1/2` for an electron that has spin-down.

Since your electron is alone in the `p_z` orbital, you can pick either value for `m_s`. Let's say that we have `m_s = +1/2`.

Therefore, you can say that a valid set of quantum numbers that describe the last electron added to an aluminium atom could be

`n=3, l=1, m_l = 0, m_s = +1/2`

This describes an electron located on the third energy level, in the 3p-subshell, in the `3p_z` orbital, that has spin-up

You could also have, for example

`n=3, l=1, m_l = -1, m_s = +1/2`

This describes an electron located on the third energy level, in the 3p-subshell, in the `3p_x` orbital, that has spin-up

`n=3, l=1, m_l = 1, m_s = +1/2`

This describes an electron located on the third energy level, in the 3p-subshell, in the `3p_y` orbital, that has spin-up

Here is a video with more explanation of quantum numbers.