Chem – Valence Electrons

What sections should I know before attempting to learn this section?

—> Protons and Electrons


What are valence electrons?

Valence electrons are the outermost electrons of the element. This overlaps with the electron shells which were described in the previous section. In fact, in many cases (but not all) the amount of electrons in the last electron shell are the same as the valence electrons. The valence electrons simply do not include the periodic groups of 3 through 12. Most people will call these groups the transition metals. When you are figuring out the valence electrons, you simply leave out groups 3 through 12. This is a periodic table link that shows the valance electrons organized on the periodic table. Below is a table of how the valence electrons match up with the different periodic table groups.


Group Valence Electrons
Group 1 1
Group 2 2
Group 13 3
Group 14 4
Group 15 5
Group 16 6
Group 17 7
Group 18 8


Examples: How many valence electrons do these elements tend to have? Look at your valence electron periodic table while figuring these out.


C 4
Br 7
Ca 2


VIDEO Valence Electrons Demonstrated Example 1: How many valence electrons does nitrogen have?


Which periodic table row is nitrogen in?

Answer: 2nd


Start counting boxes across from the first element on the second row (Li) until you get to nitrogen. How many boxes did you count?

Answer: 5


So how many valence electrons does nitrogen have?

COMPLETE ANSWER: 5 valence electrons


PRACTICE PROBLEMS: How many valence electrons do these elements tend to have?  Use the periodic table to solve.  If needed use the valence periodic table.


K 1
Se 6
Mg 2
N 3
Cs 1
I 7


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