The Periodic Table Explained (Groups, Periods, and How to Read It)
The periodic table looks intimidating, but it is really an organised map of all the elements. Its layout is not random — position tells you a lot about how an element behaves.
Groups and periods
Two directions, two meanings.
- •Groups (columns): elements in the same column have similar chemical properties and the same number of outer electrons.
- •Periods (rows): going across a row, elements gain one proton (and one electron) at a time.
Metals, non-metals, and a few special groups
Most elements are metals (left and middle); non-metals sit on the right. Group 1 (alkali metals) are very reactive; Group 7 (halogens) are reactive non-metals; Group 0/8 (noble gases) barely react at all.
Reading an element box
Each box shows the symbol, the atomic number (number of protons, which defines the element), and the atomic mass. The atomic number increases as you read left to right, top to bottom.
Frequently asked questions
What do elements in the same group have in common?
They have the same number of outer-shell electrons, which gives them similar chemical properties.
What does the atomic number tell you?
It is the number of protons in an atom, which identifies the element and sets its place in the table.