‘Physics invades the periodic table’ assesses the impact of discoveries in physics on the periodic table. Rutherford provided evidence for the nuclear structure of atoms, and also determined that the charge of an atom is equal to half its atomic weight. An amateur, Anton van den Broek, linked this principle to the number of protons in a nucleus, thus devising the notion of atomic number. Mosely quantified this principle, and used it to show exactly how many elements would fill the gaps in the periodic table. Radioactive experiments had created new forms of elements with different weights but the same charge, which Soddy identified as isotopes.