Even though each atom has roughly a whole number of atomic mass units, you will notice that the atomic mass on the periodic ... table and tend to have one valence electron and so carry a charge ...

The periodic table was arranged by atomic mass, and this nearly always gives the same order as the atomic number. However, there were some exceptions (like iodine and tellurium, see above), which didn ...

often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic number. Scientists use the periodic ...

The periodic table continues to evolve with the progress of science. In nature, only elements up to atomic number 94 exist; to go further, it was necessary to synthesise new elements in the laboratory ...