How many valence electrons does magnesium have in ir's outer shell? WHAT?!?

Question

How do u find that out?

Answer 1

Magnesium is in the second column of the periodic table so it has two valence electrons in its outer shell. (If you are doing orbitals it is 3s^2)

Answer 2

Valence electrons are electrons on the last energy level. Since magnesium has an atomic number of 12 then it contains 12 electrons. Based on electronic configuration 1s^2 2s^2 2p^6 3s^2, the last energy shell is 3s^2. So the valence electron is 2.

Answer 3

Mg. Atomic No. = 12.
The 1st shell can only carry up to 2 electrons.
The 2nd only up to 8 electrons.
The 3rd shell CAN carry up to 18 electrons.
But...As Mg has only 12 Protons and therefore, when stable, also has 12 electrons.
That's, 2 in Shell 1, + 8 in Shell 2 leaving only 2 for Shell 3....the outer shell and, the number of valence electrons.

Answer 4

You will have to use the quantum mechanical model for showing the location of the electrons in the atom.

short version:

Order of the orbitals:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, etc.

s holds 2 electrons
p holds 6 electrons
d holds 10 electrons

Magnesium is number 12 on the periodic table. This is the number of protons in Mg. Since you are dealing with a neutral atom, this is also the number of electrons you need in your model.

starting with the 1s, you fill it before moving on. S sublevels hold 2 electrons, leaving 10 to place and a partial configuration of:

1s^2

Then you move to the 2s, which is also full after 2 electrons. This leaves 8 more to place and gives our configuration:

1s^2 2s^2

Then is the 2p, which holds 6 electrons. This leaves 2 more to place.

1s^2 2s^2 2p^6

The last two get placed in the next sublevel in the sequence 3s. s sublevels hold 2 electrons, so both can go in there. This gives us a final configuration of:

1s^2 2s^2 2p^6 3s^2

The outer shell in the one with the highest big number out in front. In this case, the 3s sublevel. There are two electrons in that sublevel.

Your answer is 2.