#e <t>theory<d>1884<n>Le Chatelier's Principle<au>Le Chatelier<info>This is the thermodynamic principle that every change in a system in stable chemical equilibrium results in a rearrangement of the system so that the original change is minimised.
#e <t>disc<d>1894<n>argon<c>London<info>by William Ramsay and Lord Rayleigh
#e <t>disc<d>1900<n>radon<c>Germany<info>by Friedrich Dorn
// 20th century
#p <nat>American<o>chemist<n>Linus Pauling<b>1901 Feb 28<d>1994 Aug 19<c>California
#e <t>theory<d>1904<n>electrons in concentric rings<c>Cambridge<au>J. J. Thomson<info>J. J. Thomson theorised that atoms contain a specific number of electrons arranged in concentric rings.
#e <t>exp<d>1913<n>K-line frequency relation<c>Manchester<info>Physicist Henry Mosley discovers that the K-line's frequency depends on the square of the periodic order.
#e <t>theory<d>1913<n>nuclear charge determines periodic arrangement<c>Holland<info>Anton van den Broek determined that nuclear charge determines periodic arrangement.
#e <t>synthesis<d>1936<n>element 43, technetium<c>San Francisco<info>Technetium was first synthesised at Berkeley by Emilio G. Segrè, and then analysed by him in Palermo.