Answer:Use the K L M N shell orbit
Explanation: Valence electrons are those electrons on the outermost shell of an atomic nucleus.
The K L M N electron shell is named by a spectroscopist called Charles G. Barkla, who discovered the A X-rays ( high energy rays) and the B X-rays ( low energy rays), he later renamed the A X-rays K X-rays which is the Energy level orbit, and the B X-rays was also renamed to be the L M N and so on.
PLEASE SEE PICTURE ATTACHED
THE PICTURE SHOWS HOW TO DETERMINE VALENCE ELECTRON USING THE As AND B's WHICH ARE THE K L M N SHELL ORBIT, USING SILICON AS AN EXAMPLE.
The maximum number of electron in the K orbit is 2
The maximum number of electron in the L M N shell is 8
Therefore the number of electron found in the outermost shell becomes the number of Valence electron in that element.