The first 20 elements of the periodic table and
- the first 20 elements of the periodic table and their chemical symbols
- the first 20 elements of the periodic table and
- the first 20 elements of the periodic table and their mass number
- the first 20 elements of the periodic table and their
- the first 20 elements of the periodic table and their valency
- the first 20 elements of the periodic table and their electronic configuration
- the first 20 elements of the periodic table and their symbols
