Hydrogen
Hydrogen, the first element in the table, has an atomic number of one.
This is indicated, as with all other elements, by the number in the bottom left corner of the element's square in the periodic table.
Helium
Helium, the second element, has an atomic number of two, as indicated in the bottom left corner.
This number increases with each element, with lithium having an atomic number of three, beryllium four, and so on right through the periodic table.
Carbon
Carbon's atomic number is six. This tells you that there are six protons in the nucleus.
But it also tells you something more. Because the number of protons in an atom always equals the number of electrons, the atomic number:
