Cerium is a grey, shiny or lustrous metal. At room temperature cerium is a solid. It melts and becomes a liquid at 798C and boils and becomes a gas at 3424C. It burns in air to form a compound with one cerium atom and two oxygen atoms. 0.0046% of the Earth's crust is cerium which means that it is quite common - more common than Tin and Lead and nearly as common as zinc