Zinc is a chemical element with symbol Zn and atomic number 30. It is the first element of group 12 of the periodic table. In some respects zinc is chemically similar to magnesium: its ion is of similar size and its only common oxidation state is +2. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest mineable amounts are found in Australia, Asia, and the United States. Zinc production includes froth flotation of the ore, roasting, and final extraction using electricity (electrowinning).
How many stable isotopes does zinc have?
five

City and Guilds College was founded in 1876 from a meeting of 16 of the City of London's livery companies for the Advancement of Technical Education (CGLI), which aimed to improve the training of craftsmen, technicians, technologists, and engineers. The two main objectives were to create a Central Institution in London and to conduct a system of qualifying examinations in technical subjects. Faced with their continuing inability to find a substantial site, the Companies were eventually persuaded by the Secretary of the Science and Art Department, General Sir John Donnelly (who was also a Royal Engineer) to found their institution on the eighty-seven acre (350,000 m) site at South Kensington bought by the 1851 Exhibition Commissioners (for GBP 342,500) for 'purposes of art and science' in perpetuity. The latter two colleges were incorporated by Royal Charter into the Imperial College of Science and Technology and the CGLI Central Technical College was renamed the City and Guilds College in 1907, but not incorporated into Imperial College until 1910.
Which college was founded in 1876?
City and Guilds College

Several dozen radioisotopes have been characterized. 65Zn, which has a half-life of 243.66 days, is the most long-lived radioisotope, followed by 72Zn with a half-life of 46.5 hours. Zinc has 10 nuclear isomers. 69mZn has the longest half-life, 13.76 h. The superscript m indicates a metastable isotope. The nucleus of a metastable isotope is in an excited state and will return to the ground state by emitting a photon in the form of a gamma ray. 61Zn has three excited states and 73Zn has two. The isotopes 65Zn, 71Zn, 77Zn and 78Zn each have only one excited state.
What does the superscript "m" indicate?
metastable isotope