Valence Electrons

You know how atoms can link together? Well, these’re what let them do that and what says how many they can link to, too. The valence electrons are just the outside layer, atoms can give, take and share them. Check this out, you can tell how many an atom has just by looking at the periodic table.

The first column has one valence electron, all the ones from the second to the twelfth have 2, and the rest have 10 less than the column they’re in. That means an empty outer layer has 0 and a full outer layer has 8… Well, except for the first row, the hydrogen and helium, they can have either 0 or 2. All the atoms want either an empty or full outer layer, so they link to other atoms (it’s actually called a bond). Depending on what you have, the atoms can make up to 3 bonds to any other atom. Watch this, we have water, 2 atoms of hydrogen and 1 of oxygen.

Each hydrogen has 1 valence electron

And each oxygen has 6

Each hydrogen wants one and the oxygen wants two. How do we do this? Why, let’s have them share. The hydrogens bond to the oxygen, and everyone’s happy, all the atoms have full outer layers and I have something to drink.

…But hydrogen’s the only atom left of carbon that wants more electrons. The others are looking to get rid of their electrons. This time we use the kind of salt you put on food (there’re actually other kinds, too).

Sodium has one valence electron

And chlorine has 7

The sodium wants to get rid of one and the chlorine wants to find one more, so the chlorine takes the sodium’s electron. Now the sodium emptied its outer shell and the chlorine has a full one because they bonded together.