How many electrons does it take to fill the n-level of an atom?

Question

I am a high school teacher at a private Christian school and our Science books inform the students that 2 electrons fill the k-level in the electron orbitals, 8 fill the l-level, and 8 fill the m-level. However, it doesn't specify how many it takes to fill the next level and I'm wondering if it's different for the different types of atoms. Anyone know? Can you clarify it for me so I can clarify it for my student?

Answer 1

As another poster noted, this is a gross oversimplification, but if we ignore the transition elements we can pretend that the first orbital holds 2 electrons, the second and third hold 8 each, the fourth and fifth hold 18 each, and the sixth and seventh hold 32 each. This simplification explains why there are two elements on the first row of the periodic table, eight on each of the next two, and 18 on the subsequent rows (plus 14 extras in the Lanthanide and Actinide series).

At the high school level what students should probably know is that this simplification is useful, though far from complete, and that it does a good job of explaining the behavior of elements near the left and right edges of the periodic table but is hopeless at the middle.

Answer 2

I'm afraid the K,L,M model of electronic configuration is a gross over-simplification; bordering on a complete lie. It is taught because it holds true for the early elements in the periodic table, which is presumably deemed to be all that is required for the high school syllabus.

The actual electronic configuration for elements goes like this, in order of filling:
There's '1s' orbital, which is spherical, and can hold a pair of electrons. (Your 'K' level).

A '2s' orbital, also spherical and can hold a pair of electrons.

3 '2p' orbitals, each of which are 'dumbell' shaped and can each hold a pair of electrons.
(The 2s and 2p orbitals make up your 'L' level)
A 3s orbital, again, spherical, holding up to 2 electrons.

3 '3p' orbitals, each holding a pair of electrons.

5 '3d' orbitals, each holding a pair.

It goes on in this fashion, including 'f' orbitals next, but there are now some complications:

In principle, the orbitals should fill in the order I've written them. However, the 3d orbitals will not fill until the 4s orbital has filled. After the 4s has filled, the 3d will fill, but once the 3d is occupied, the electrons in the 4s orbital must be regarded as being in the 3d orbital instead, while the 4s orbital is deemed to be unoccupied. elements that involve electrons in the 'd'-orbitals are 'transition metals', and have variable oxidation states and all kinds of other complications to make life confusing.

Anyway, the filling order prior to transition metals is simple enough, and is as follows;
1s- 2 electrons
2s -2 electrons
2p -6 electrons
3s -2 electrons
3p -6 electrons
(3d- ignore!!!!!!!!!)
4s- 2 electrons.
That takes you up to calcium. Beyond that are the transition metals, which I recommend avoiding. however, it is worth noting that all subsequent group 1 and group 2 metals have a valence 's'-shell- 5s, 6s, etc, and thus are chemically similar to their equivalents further up the table. Furthermore, all halogens have a valence 'p' shell, in need of one more electron to fill it. The 5 full 'd' shells in between on each period that make up the transition block contain 10 electrons.

Answer 3

16 electron if i am not wrong i have read 9 yrs ago in high school so i am telling.