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A dermatologist is a...
“A dermatologist is a flesh man.”
What hides this stereogram?
Brain Teasers
[2847] What hides this stereogram? - Stereogram - 3D Image - #brainteasers #stereogram #3Dimage
2016-10-02
FranciumIn 1930, the element Fr (francium) was discovered, the last naturally occurring element to be found. It is the heaviest alkali metal atom, with atomic number 87. Marguerite Pereyjoined (Oct 1929) the Institut du Radium in Paris in Oct 1929 as a technician for Marie Curie. Perey worked for years on actinium, which was anticpated to produce the new element by alpha decay. Finally, she was able to make thefirst entry about francium in her lab notebook on 7 Jan 1939, recording its half-life as about 20 minutes. A note in the Comptes Rendus was presented at the Académie des Sciences by Jean Perrin (9 Jan 1939). In his periodic table, Mendeleev anticipated its discovery, and provisionally named it eka-cesium. Perey gave it the name “francium.” She first used the symbol Fa, but changed it to Fr.«[Previously on this site as discovered 11 Jan 1930.] |