Barium fluoride Barium fluoride Barium fluoride (BaF) is a chemical compound of barium and fluorine and is a salt. It is a solid which can be a transparent crystal. It occurs in nature as the mineral frankdicksonite. The solid adopts the fluorite structure and at high pressure the PbCl structure. In the vapor phase the BaF molecule is non-linear with an F-Ba-F angle of approximately 108°. This is an exception to VSEPR theory which would predict a linear structure. Ab initio calculations have been cited to propose that contributions from d orbitals in the shell below the valence shell are responsible. Another
Pewter Pewter Pewter () is a malleable metal alloy. It is traditionally composed of 85–99% tin, mixed with copper, antimony, bismuth, and sometimes silver or lead, although the use of lead is less common today. Copper and antimony act as hardeners while lead is more common in the lower grades of pewter, which have a bluish tint. Pewter has a low melting point, around , depending on the exact mixture of metals. The word "pewter" is probably a variation of the word "spelter", a term for zinc alloys (originally a colloquial name for zinc). Pewter was first used around the beginning