I though I could help you but then:
ENGLISH SCIENTIFIC WORDS EVERYWHERE.
I gave up.
Sorry.
but.. this is.... basic.. chemi- *breaks down crying*
naw, i asked on a chemistry forum and i got the answer straight off. gotta love nerds. <3
Valence electrons are electrons in the outermost energy level, which is also the outermost shell.
When you are looking at an electron configuration, let's say the one for chlorine, the letters represent the subshell, or the shape of the orbitals. The numbers in front of the letters represent the energy level of the subshell. So for chlorine, we can see that it has electrons in three energy levels by looking at its electron configuration.
Since valence electrons are electrons in the outermost energy level, all you have to do is determine the outermost energy level and then count the number of electrons in it.
For chlorine, the outermost energy level is 3, so we just count the electrons in all the orbitals preceded by the number 3. There are 2 in the 3s orbital and 5 in the 3p orbitals, giving a total of 7 valence electrons.
For calcium, if you wrote out the electron configuration, the highest energy level would be 4, and the only occupied orbital in the 4th energy level would be the 4s orbital. Since there are 2 electrons in the 4s orbital and none in the 4p orbitals, there are only 2 electrons in the entire 4th energy level. Therefore, there are 2 valence electrons in calcium.
note: obviously, clicking on the hyperlink on top of the second quote gets you nowhere, as it is on a different forum