Full Idea
By using X-rays, Henry Moseley later discovered that a better ordering principle for the periodic system is atomic numbers rather than atomic weight, by subjecting many different elements to bombardment.
Gist of Idea
Moseley, using X-rays, showed that atomic number ordered better than atomic weight
Source
Eric R. Scerri (The Periodic Table [2007], 06 'Intro')
Book Reference
Scerri,Eric R.: 'The Periodic Table' [OUP 2007], p.159
A Reaction
Moseley was killed in the First World War at the age of 26. It is interesting that they more or less worked out the whole table, before they discovered the best principle on which to found it.
Related Ideas
Idea 17410 Moseley showed the elements progress in units, and thereby clearly identified the gaps [Scerri]
Idea 17411 If all elements are multiples of one (of hydrogen), that suggests once again that matter is unified [Scerri]