Properties and Reactions — Tech Evolutions

Entry	Year	Description	Impact
N/A (Scientific Evolution)	Throughout 20th Century	While there are no constitutional amendments for scientific principles, the understanding of elemental properties has undergone significant 'amendments' or refinements through scientific discovery. A key evolution was the shift from classifying elements purely by atomic weight (Mendeleev) to atomic number (Moseley). This refinement, based on the number of protons, provided a more accurate and consistent basis for the periodic law, resolving anomalies in Mendeleev's original table where elements like Argon and Potassium seemed out of order by weight but fit perfectly by atomic number. This change solidified the fundamental link between atomic structure and chemical properties.	This shift provided a more robust and theoretically sound basis for the periodic table, allowing for a more precise understanding and prediction of metallic and non-metallic properties. It confirmed that the number of electrons (which equals the atomic number in a neutral atom) is the primary determinant of an element's chemical behavior, including its reactivity and tendency to form specific types of bonds. This underpins all modern chemical understanding of metals and non-metals.