Tin is a Block P, Group 14, Period 5 element. The number of electrons in each of Tin's shells is 2, 8, 18, 18, 4 and its electronic configuration is [Kr] 4d¹⁰ 5s² 5p². In its elementa form tin's CAS number is 7440-31-5. The tin atom has a radius of 140.5.pm and it's Van der Waals radius is 217.pm. Tin compounds sprayed onto glass are used to produce electrically conductive coatings. These have been used for panel lighting and for frost-free windshields. Most window glass is now made by floating molten glass on molten tin (float glass) to produce a flat surface. Crystalline tin-niobium alloy is superconductive at very low temperatures. This promises to be important in the construction of superconductive magnets that generate enormous field strengths but use practically no power. Tin is the basis for many eutectic alloys and the discovery by early man that copper could be better formed and crafted if tin were added producing the first bronze and launching what we refer to as the "Bronze Age" and the first Neolithic metal tools, cooking utensils, and jewelry produced from rudimentary bronze. An important tin compound is the chloride, which is used as a reducing agent and as a mordant in calico printing.  Tin is also used in various metal alloys (See AE Alloys). Tin was first discovered by Early Man.