The Atom

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was much more massive
remainder that was positively charged, Thomson went on in the next decade to
develop a model of the atom that came to be called the "plum pudding" model.
The Thomson atom, "a number of negatively electrified corpuscles enclosed in a
sphere of uniform positive electrification" like raisins in a pudding, was a
hybrid: particulate electrons and diffuse remainder. It served the useful
purpose of demonstrating mathematically that electrons could be arranged in a
stable configurations within an atom and that the mathematically stable
arrangements could account for the similarities and regularities among chemical
elements that the periodic table of the elements displays. It was becoming
clear that the electrons were responsible for chemical affinities between
elements, that chemistry was ultimately electrical.
Thomson just missed discovering X rays in 1884. He was not so unlucky
in legend as the Oxford physicist Frederick Smith, who found that ...

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the fluorescence
glass, which immediately suggested to him that he should test various
fluorescence materials to see if they also emitted X rays. He worked for ten
days without success, read an article on X rays in January 30 that encouraged
him to keep working and decided to try a uranium slat, uranyl potassium sulfate.
His first experiment succeeded-he found that the uranium salt emitted
radiation but misled him. He had sealed a photographic plate in black paper,
sprinkled a layer of uranium salt onto the paper and "exposed the whole thing to
the sun for several hours." When he developed the photographic plate "I saw the
silhouette of the phosphorescent substance in black on the ...

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