After the third energy level has 8 electrons, the next electron goes into the fourth level. 4th Period: Potassium and Calcium—Electrons go into the fourth energy level. A small piece of sodium metal ...

So, today we're going to look at the periodic table. That thing that you see behind ... For example, lithium (Li), sodium (Na) and potassium (K) all have the same kind of reaction with water.

They include lithium, sodium and potassium, and are placed in the first vertical column on the left of the periodic table. All the Group 1 elements are very reactive, and all react with water to ...