The history of the chemical elements – An elemental chronology compiled by David Bradley back in 2004
Ancient Times – gold, silver copper iron lead tin mercury sulfur carbon
Time of the Alchemists – arsenic, antimony
13th Century India – zinc
1669 phosphorus
1737 cobalt (~1735)
1741 platinum (1735)
1751 nickel
1753 bismuth
1755 magnesium (1775)
1766 hydrogen
1772 nitrogen
1774 oxygen, chlorine, manganese
1778 molybdenum
1782 tellurium
1783 tungsten
1789 uranium (1841)
1789 zirconium
1793 strontium (1808)
1794 yttrium
1797 titanium (1791)
1797 chromium
1798 beryllium
1801 vanadium, niobium
1802 tantalum
1803 cerium, rhodium, palladium, osmium, iridium
1807 potassium, sodium
1808 calcium, barium
1811 iodine
1817 lithium, cadmium, selenium
1823 silicon (1824)
1825 aluminum/aluminium (1827)
1826 bromine
1828 thorium
beryllium
1839 lanthanum
1843 terbium, erbium
1844 ruthenium
1860 caesium/cesium (rubidium)
1861 rubidium, thallium
1863 indium
1868 helium, boron
1875 gallium
1878 ytterbium
1879 thulium, scandium (1878), holmium (1878), samarium
1880 gadolinium
1885 praseodymium, neodymium
1886 germanium, fluorine (1866), dysprosium
1894 argon
1898 neon, krypton, xenon, radon, polonium,
1899 actinium
1901 europium (1890)
1907 lutetium
1917 protactinium (1913)
1923 hafnium
1925 rhenium
1937 technetium
1939 francium
1940 astatine, neptunium (plutonium)
1941 plutonium (1940)
1944 curium
1945 americium (1944), promethium
1949 berkelium
1950 californium
1952 einsteinium
1953 fermium (1952)
1955 mendelevium
1958 nobelium
1961 lawrencium
1964 rutherfordium
1970 dubnium (1967)
1974 seaborgium
1976 bohrium (1975)
1982 meitnerium
1984 hassium
1994 darmstadtium, unununium
1996 ununbium
1999 ununquadium
2004 ununtrium, ununpentium – read about the discoveries of the most recent chemical elements.
For a list complete with details of the discoveries try the Wikipedia entry or the About site, there are discrepancies between the two, however (see bracketed entries above) and I’d say the only definitive elemental data online is provided by Mark Winter’s WebElements.