Atomic number

1911

Atomic number

The book of science

Tom Sharp

Antonius van den Broek chemistry

Atomic number

Atomic parts

Z

Dmitri Mendeleev tried to order the first periodic table according to ascending atomic weights; however, he had to place tellurium ahead of iodine, even though tellurium has the greater atomic weight, to better align the chemical properties of the two with the chemical properties of the elements above them. The modern periodic table is arranged by atomic number.

Francis William Aston discovered isotopes in 1922, and James Chadwick discovered the neutron in 1932.

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