What is It Key Points
The atomic number is the number of protons (positively charged
particles) in an atom.
In 1913, Henry Gwyn-Jeffreys Moseley was an English physicist
who demonstrated that the atomic number, the number of protons
in an atom, determines most of the properties of an element.
In 1919, Ernest Rutherford successfully carried out a nuclear
transmutation reaction a process of transforming one element
or isotope into another element.
In 1925, there were four unknown elernents in the periodic table
that corresponds to atomic numbers 43, 61, 85, and 87. Elements
with atomic numbers 43 and 85 were synthesized using particle
accelerators.
A particle accelerator is a device that is used to speed up the protons
to overcorne the repulsion between the protons and the target atomic
nuclei by using magnetic and electrical fields. It is used to
synthesize new elements.​