If the chemical symbol consists of more than one letter, any subsequent letters are lowercase. Example: Hydrogen → H, Helium → He 118 Elements and Their Symbols and Atomic Numbers ...

The atomic number is shown below the chemical symbol, and the mass number is shown above. In this example the atomic number is 17 and the mass number is 35. This means that each of these atoms has: ...

Chemists use symbols and formulae to represent ... elements are in order of atomic number in periods and groups. Electronic structures model how electrons are arranged in atoms.