compounds (the stable state for silver; less so for copper) they are typical B-subgroup metals. In their +2 and +3 states their chemistry is typical of transition metal compounds. Pseudo metals and hybrid metals The B-subgroup metals can be subdivided into pseudo metals and hybrid metals. The pseudo metals (groups 12 and 13, including boron) are said to behave more like true metals (groups 1 to 11) than non-metals. The hybrid metals As, Sb, Bi, Te, Po, At — which other authors would call metalloids — partake about equally the properties of both. The pseudo metals can be considered related to the hybrid metals through the group 14 carbon column. Base metals Mingos writes that while the p-block metals are typical, that are not strongly reducing and that, as such, they are base metals requiring oxidizing acids to dissolve them. Borderline metals Parish writes that, 'as anticipated', the borderline metals of groups 13 and 14 have non-standard structures. Gallium, indium, thallium, germanium, and tin are specifically mentioned in this context. The group 12 metals are also noted as having slightly distorted structures; this has been interpreted as evidence of weak directional (i.e. covalent) bonding. Chemically weak metals Rayner-Canham and Overton use the term chemically weak metals to refer to the metals close to the metal-nonmetal borderline. These metals behave chemically more like the metalloids, particularly with respect to anionic species formation. The nine chemically weak metals identified by them are beryllium, magnesium, aluminium, gallium, tin, lead, antimony, bismuth, and polonium. Frontier metals Vernon uses the term "frontier metal" to refer to the class of chemically weak metals adjacent to the dividing line between metals. He notes that several of them "are further distinguished by a series of…knight's move relationships, formed between one element and the element one period down and two groups to its right." For example, copper(I) chemistry resembles indium(I) chemistry: "both ions are found mostly in solid-state compounds such as CuCl and InCl; the fluorides are unknown for both ions while the iodides are the most stable." The name frontier metal is adapted from Russell and Lee, who wrote that, "…bismuth and group 16 element polonium are generally considered to be metals, although they occupy 'frontier territory' on the periodic table, adjacent to the nonmetals." Fusible metals Cardarelli, writing in 2008, categorizes zinc, cadmium, mercury, gallium, indium, thallium, tin, lead, antimony and bismuth as fusible metals. Nearly 100