Period 5 element blood cells in the body. Tin is a chemical element with the symbol Sn (for ) and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table. Tin is obtained chiefly from the mineral cassiterite, where it occurs as tin dioxide, SnO. This silvery, malleable
SN 2003gd SN 2003gd, and which is believed to be the supernova's progenitor star. This progenitor star was a red supergiant, consistent with the expectations of existing single-star stellar evolution models. It is the first progenitor of a normal type II-P supernova to have ever been detected. SN 2003gd SN 2003gd was a type II-P supernova occurring in the spiral galaxy Messier 74 in the constellation Pisces. SN 2003gd was discovered on 12 June 2003 by Robert Evans, using a 0.31m reflector, and its discovery was confirmed on 13 June 2003 by R. H. McNaught using the 1.0m telescope at the Siding