Question

One of the outermost electrons in a strontium atom in the ground state can be described by what sets of four quantum numbers?

Answer 1

Here's what I got.

Explanation:

Your starting point for this problem will be the electron configuration for a neutral strontium atom in its ground state, which looks like this

`"Sr: " 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 color(red)(5)s^2`

As you can see, strontium's outermost electrons are located on the fifth energy level, in the 5s-orbital.

In order to completely describe these two electrons, you need to list the values of the four quantum numbers used to characterize their location and spin.

![figures.boundless.com]()

So, you know that the two electrons are located on the fifth energy level, which means that the principal quantum number, `n`, will be equal to `color(red)(5)`.

The angular momentum quantum number, `l`, which describes the subshell in which the electrons reside, will take the value specific for the s-subshell, i.e. `l` will be equal to `0`.

For the s-subshell, the magnetic quantum number, `m_l`, can only take one possible value, and that is `m_l = 0`. Here `m_l = 0` describes the s-orbital found in the s-subshell.

Finally, the spin quantum number, `m_s`, can take two possible values, `m_2 = +- 1/2`.

Since two electrons occupy the 5s-orbital, one will have `m_s = 1/2`, which describes spin-up, and the other `m_s = -1/2`, which describes spin-down.

Therefore, the quantum sets that describe the two outermost electrons electrons in a strontium atom will be

`n=5, l=0, m_l = 0, m_s = +1/2`

and

`n=5, l=0, m_l = 0, m_s = -1/2`