Quark
The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964. Quarks were introduced as parts of an ordering scheme for hadrons, and there was little evidence for their physical existence until deep inelastic scattering experiments at the Stanford Linear Accelerator Center in 1968. Accelerator experiments have provided evidence for all six flavors. The top quark, first observed at Fermilab in 1995, was the last to be discovered.
Bernard Courtois
Courtois was acknowledged by Humphry Davy and Joseph Louis Gay-Lussac as the true discoverer of iodine. He went into manufacturing high-quality iodine and its salts in 1822. In 1831 he was awarded 6,000 francs as part of the Montyon Prize by "L'Academie royale des sciences" for the medicinal value of this element. He struggled financially for the rest of his life and died September 27, 1838. He was 62 years old and had no assets left for his widow or son. In the year of his death, the "Journal de chimie médicale" drily noted his passing under the heading Obituary as:"Bernard Courtois, the discoverer of iodine, died at Paris the 27th of September, 1838, leaving his widow without fortune. If, on making this discovery, Courtois had taken out a certificate of invention, he would have realized a large estate."