The next thing to remember is:2

Then remember: 4

The s sub-shell can have, at most, 2 electrons

The p sub-shell can have at most 2+ 4 = 6 electrons

The d sub-shell can have at most 6 + 4 = 10 electrons

I think you can guess how many electrons there can be in the f sub-shell.

Now, for the s shell. With one exception, you fill the s sub-shell in the group 1A and 2A groups. The one exception is He, Get out your periodic table and follow along…

H is 1s^1

He is 1s^2

Li is 1s^2 2s^1

Can you guess Be?

Now jump across to B.

B is 1s^2 2s^2 2p^1

Can you fill in the rest through Ne?

The 3rd row (period) starts with Na. Can you get through the period, and continue into the 4th period to Ca?

But what to do with Sc?

Try: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1

3^d1???

Yup!

Consider this chart:

1s^2

2s^2 2p^6

3s^2 3p^6 3d^10

4s^2 4p^6 4d^10 4f^14

5s_________________g^__

6______________________h__

Just write it out on a piece of paper, fill in the blanks

Now, draw a diagonal arrow through 1s^2, starting from the upper left corner, down to the lower right corner.

Parallel to that line, draw another through 2s^2 (this is going somewhere, I promise)

The third line goes through 2p^6 and 3s^2.

Now a fourth line, this one goes through 3p^6 and 4s^2.

The fifth line (drum roll) goes through 3d^10, 4p^6, and 5s^2.

Now, if you can follow the pattern to here (which got us to Sr!), what is the next subshell to fill?

Draw another line through the chart, parallel to the others (hint: start at 4d^10, and draw down to 6s^2.

This means that Y ends with 4d^1

Follow along with the periodic table, do you see the d orbitals are the transition elements?

Where in the periodic table are the f orbitals?

There is one other exception… In the 3d^10 subshell, the electrons do not fill in order, but I can not remember the details of that particular exception.

Go through this one more time, and you should be able to write out the full electron configuration of any element.

Good luck!