Question #9b3cf

1 Answer

Answer:

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.

figures.boundless.com

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.