physical science
Storyboard Text
- JHOSEPH J. THOMSON With J. J. Thomson dicovery of electron in 1897 it became clear that atoms were not the smallest building blocks of nature.
- In 1897 Thomson showed that cathode ray were compose of previously unknown negatively charged particles (now called electrons) which he calculated must have bodies much smaller than atoms and a very large charge -to-mass ratio
- Thomson is also credited with finding the first evidince for isotopes of a stable (non-radio active) element in 1913 as part of his exploration into the composition of canal rays (positive ions)
- The plum pudding is one of tseveral historical scientific model of atom.
- First propose by J. J. Thomson in 1904 soon after the discovery of electron, but before the discovery of atomic nucleus, the model tried to explain two properties of atoms then known: that electrons are negatively charged particles and that atoms have-
- no net electric charge. The plum pudding models has electrons surrounded by a volume of positive charge, like negatively charged "plum" embedded in a positively charged "pudding'
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