When did Moseley arrange the periodic table?
Using atomic number instead of atomic mass as the organizing principle was first proposed by the British chemist Henry Moseley in 1913, and it solved anomalies like this one. Iodine has a higher atomic number than tellurium - so, even though he didn't know why, Mendeleev was right to place it after tellurium after all!
Today, we know that the atomic number gives the number of protons (positive charges) in the nucleus. This was the discovery made by Henry Gwyn-Jefferies Moseley. He found that certain lines in the X-ray spectrum of each element moved the same amount each time you increased the atomic number by one.
- The elemenents of the periodic table sorted by atomic mass
Atomic Mass Name chemical element Atomic number 1.0079 Hydrogen 1 4.0026 Helium 2 6.941 Lithium 3 9.0122 Beryllium 4
- The actinide family is comprised of fifteen elements that start with actinium (Ac) at atomic number 89 and finish up with lawrencium (Lr) at number 103. It's doubtful your teachers will ever ask you to remember all of the elements in the series.
- the law that the properties of the elements are periodic functions of their atomic numbers. Also called Mendeleev's law. (originally) the statement that the chemical and physical properties of the elements recur periodically when the elements are arranged in the order of their atomic weights.
When Moseley arranged the elements in the periodic table by their number of protons rather than their atomic weights, the flaws in the periodic table that had been making scientists uncomfortable for decades simply disappeared.
- Henry Gwyn Jeffreys Moseley (23 November 1887 – 10 August 1915) was an English physicist, whose contribution to the science of physics was the justification from physical laws of the previous empirical and chemical concept of the atomic number. This stemmed from his development of Moseley's law in X-ray spectra.
- Today, we know that the atomic number gives the number of protons (positive charges) in the nucleus. This was the discovery made by Henry Gwyn-Jefferies Moseley. He found that certain lines in the X-ray spectrum of each element moved the same amount each time you increased the atomic number by one.
- Dmitri Mendeleev
Updated: 29th September 2018