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How to Count the Valance Electrons of an Element

The valency of an atom determines the ability for one element to bond with other elements. Although counting the electrons that make up the outer-most layer of the atomic structure is impossible with the naked eye, you can use the atomic number on the periodic table to establish the number of electrons on each atom's layer. With scientific knowledge of the atomic structure and how to calculate valency, you can count the valence electrons of any atom on the periodic table.

Instructions

- 1
  Find the atomic number for the element for which you are calculating the valency. The atomic number for each element can be found on the periodic table and is labeled in numerical sequential order from left to right, beginning from the first row and down.
- 2
  Understand the basic structure of the electron shells that surround the nucleus of an atom. The inner-most shell layer can only hold two electrons, while each layer beyond the inner-most layer can hold up to eight electrons.
- 3
  Count the number of electrons on the outer shell layer of the atom. If the atom only has one layer, count the number of electrons on that layer. For example, the atomic number for oxygen is eight, meaning the atom has eight electrons (two in the inner layer and six in the outer-most layer).
- 4
  Count the valence electrons by assessing the number of electrons on the outer-most layer. If the outer layer has four or fewer electrons, the valency is the number of electrons on the outer layer. For example, since carbon has six electrons, two on the inner-layer and four on the outer-most layer, the valence is simply four. If the outer layer has five to eight electrons, the valency is represented by subtracting the number of electrons by eight. For example, since oxygen has six electrons on the outer-most layer, the valency is two (8 - 6 = 2).

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