Tin bent, a crackling sound known as the "tin cry" can be heard from the twinning of the crystals. Tin melts at low temperatures of about , the lowest in group 14. The melting point is further lowered to for 11 nm particles. β-tin (the metallic form, or white tin, BCT structure), which is stable at and above room temperature, is malleable. In contrast, α-tin (nonmetallic form, or gray tin), which is stable below , is brittle. α-tin has a diamond cubic crystal structure, similar to diamond, silicon or germanium. α-tin has no metallic properties at all because its atoms form
Gift Gift A gift or a present is an item given to someone without the expectation of payment or anything in return. An item is not a gift if that item is already owned by the one to whom it is given. Although gift-giving might involve an expectation of reciprocity, a gift is meant to be free. In many countries, the act of mutually exchanging money, goods, etc. may sustain social relations and contribute to social cohesion. Economists have elaborated the economics of gift-giving into the notion of a gift economy. By extension the term "gift" can refer to any item