Predicting the Number of Valence Electrons

Valence Electrons are all of the electrons which take part in reactions. They are also known as "Reactable Electrons". They are located in the outermost open shell of an atom. The highest  shell. In other words, if you had 6s24f145d106p2, you would only have 4 valence electrons, since you would only count the ones in the 6th orbital.


Here are some new terms to learn:
Open Shell: Shell containing less than the maximum number of electrons.
Closed Shell: Shell that contains exactly the maximum number of electrons.


So, in a nutshell (so punny, I know), valence electrons are all of the electrons in an atom except for the filled shell.
*Note: This excludes full d and f shells.

Don't you wish you were one of these shells instead
of learning about scientific shells? I digress.

Examples:
Sc = [Ar]4s23d1 = 2 Valance Electrons
Tl = [Xe]6s24f145d106p1 = 3 Valence Electrons (do not count full f and d shells)


All Noble Gases have 8 or 0 Valance Electrons. Whichever you prefer to write.


Now wasn't that quick and easy? Lovely. I don't even think that a video is needed... Jokes! Of course I have a video for you!

My favourite lady...