1913 ⟶ Atomic Number Concept Introduced
Henry Moseley, working from Van den Broek's earlier idea, in...
Year
1864
1911
1913
🎵 Newlands Proposes Law of Octaves
John Newlands proposes the law of octaves, a precursor to the periodic law.⟶
Law of OctavesPeriodic LawChemistryJohn NewlandsElement Classification19th Century SciencePeriodic Table
United Kingdom🗓️ Lothar Meyer Develops Early Periodic Table
Lothar Meyer develops an early version of the periodic table, with 28 elements organized by valence.⟶
Periodic TableChemistryLothar MeyerElement Classification19th Century SciencePeriodic LawValenceChemical Elements
Germany⚛️ van den Broek Proposes Organization by Atomic Number
Antonius van den Broek proposes the idea that the elements on the periodic table are more properly organized by positive nuclear charge rather than atomic weight.⟶
ChemistryPeriodic TableAtomic Numbervan den BroekElements
Netherlands🔢 Atomic Number Concept Introduced
Henry Moseley, working from Van den Broek's earlier idea, introduces concept of atomic number to fix inadequacies of Mendeleev's periodic table, which had been based on atomic weight.⟶
Atomic NumberPeriodic TableHenry MoseleyAtomic PhysicsChemistryPeriodic LawEarly 20th Century Chemistry
United Kingdom⚛️ Concept of Isotopes Proposed
Frederick Soddy proposes the concept of isotopes, that elements with the same chemical properties may have differing atomic weights.⟶
IsotopesRadioactivityFrederick SoddyNuclear ChemistryAtomic PhysicsEarly 20th Century Chemistry
United Kingdom🔢 Atomic Number Defined
Henry Moseley: defined atomic number⟶
Atomic NumberMoseleyPeriodic TableAtomic PhysicsChemistryEarly 20th Century Chemistry
United Kingdom