How to Find Valence Electrons

Part 1 of 4: Understanding Electron Shells

1. Obtain a periodic table of elements. This is a color-coded table containing squares, each of which gives an element's 1- to 3-letter symbol and its atomic number.

Part 2 of 4: Understanding Electron Shells

2. Read the atomic number of an element. The atomic number appears above the element symbol in the square. For instance, boron (B) has an atomic number of 5, meaning that it has 5 protons and 5 electrons.

Part 3 of 4: Understanding Electron Shells

3. Draw a simple diagram of an atom and place the electrons in orbits surrounding it. These orbits are called shells. The maximum number of electrons that can be in the same shell is fixed, and they are filled from the closest to farthest orbit. K Shell (closest): 2 electrons maximum. L Shell: 8 electrons maximum. M Shell: 18 electrons maximum. N Shell: 32 electrons maximum. O Shell: 50 electrons maximum. P Shell (farthest): 72 electrons maximum.

Part 4 of 4: Understanding Electron Shells

4. Find the number of electrons in the outermost shell. These are the valence electrons. - If the valence shell is full, then the element is inert. - If the valence shell isn't full, then the element is reactive, which means that it can form a bond with an atom of another element. Each atom shares its valence electrons in an attempt to complete its own valence shell.