Tecken | I |
Atomnummer | 53 |
Grupp | 17 (Halogener) |
Period | 5 |
Block | p |
Ämnesklass | Icke-metall |
Utseende | Lustrous metallic gray, violet as a gas |
Färg | Skiffer grå |
Antal protoner | 53 p+ |
Antal neutroner | 74 n0 |
Antal elektroner | 53 e- |
Fas vid STP | Fast |
Densitet | 4.933 g/cm3 |
Relativ atommassa | 126.904 u |
Smältpunkt | 386.85 K 113.7 °C 236.66 °F |
Kokpunkt | 457.4 K 184.25 °C 363.65 °F |
Ångbildningsvärme | 20.9 kJ/mol |
Elektronegativitet (Paulingskalan) | 2.66 |
Elektronaffinitet | 295.153 kJ/mol |
Oxidationstal | −1, +1, +3, +4, +5, +6, +7 (a strongly acidic oxide) |
Jonisationspotential |
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Upptäckt och första isolation | Bernard Courtois (1811) |
Namngivare | Joseph Louis Gay-Lussac (1813) |
Upptäckten av jod In 1811, iodine was discovered by French chemist Bernard Courtois. He once added excessive sulfuric acid when making Saltpetre and a cloud of purple vapour rose. He noted that the vapour crystallised on cold surfaces, making dark crystals. Courtois suspected that this material was a new element but lacked funding to pursue it further. Courtois gave samples to his friends, Charles Bernard Desormes and Nicolas Clément, to continue research. He also gave some of the substance to chemist Joseph Louis Gay-Lussac, and to physicist André-Marie Ampère. On 29 November 1813, Desormes and Clément made Courtois' discovery public. They described the substance to a meeting of the Imperial Institute of France. On 6 December, Gay-Lussac announced that the new substance was either an element or a compound of oxygen. Gay-Lussac suggested the name "iode", from the Ancient Greek ἰοειδής (ioeidēs, "violet"), because of the colour of iodine vapor. Ampère had given some of his sample to English chemist Humphry Davy, who experimented on the substance and noted its similarity to chlorine. Davy sent a letter dated 10 December to the Royal Society of London stating that he had identified a new element. Arguments erupted between Davy and Gay-Lussac over who identified iodine first, but both scientists acknowledged Courtois as the first to isolate the element. |