Post-transition metal packing structure. Tin forms Zintl phases such as NaSn, BaSn, KSn and CaSn. It has good corrosion resistance in air on account of forming a thin protective oxide layer. Pure tin has no structural uses. It is used in lead-free solders, and as a hardening agent in alloys of other metals, such as copper, lead, titanium and zinc. Lead is a soft metal (MH 1.5, but hardens close to melting) which, in many cases, is unable to support its own weight. It has a close-packed structure (BCN 12) but an abnormally large inter-atomic distance that has been attributed to partial
Solder joint over time. Solder used in making electrical connections also needs to have favorable electrical characteristics. Soft solder typically has a melting point range of , and is commonly used in electronics, plumbing, and sheet metal work. Alloys that melt between are the most commonly used. Soldering performed using alloys with a melting point above is called "hard soldering", "silver soldering", or brazing. In specific proportions, some alloys can become eutectic — that is, their melting point is the same as their freezing point, and the alloy's melting point is lower than that of either component. Non-eutectic alloys have markedly