The order of the table
118 elements, arranged by **increasing atomic number **. Mendeleev, in 1869, had ordered them by atomic mass; today is what counts.
7 min
A first look at the periodic table
Periods, groups, four families to know — and how an element's column announces the ion it forms.
The essentials
2
Periods and groups
Members only
3
Four families to know
Members only
4
Why a column is alike
Members only
5
Metals and non-metals
Members only