other metals (see also, for example, Taylor et al.). 'Other' in this sense has the related meanings of, 'existing besides, or distinct from, that already mentioned' (that is, the alkali and alkaline earth metals, the lanthanides and actinides, and the transition metals); 'auxiliary'; 'ancillary, secondary'. According to Gray there should be a better name for these elements than 'other metals'. p-block metals The p-block metals are the metals in groups 13‒16 of the periodic table. Usually, this includes aluminium, gallium, indium and thallium; tin and lead; and bismuth. Germanium, antimony and polonium are sometimes also included, although the first two are commonly recognised as metalloids. The p-block metals tend to have structures that display low coordination numbers and directional bonding. Pronounced covalency is found in their compounds; the majority of their oxides are amphoteric. Aluminium is an undisputed p-block element by group membership and its [Ne] 3s2 3p1 electron configuration, but aluminium does not literally come after transition metals unlike p-block metals from period 4 and on. The epithet "post-transition" in reference to aluminium is a misnomer, and aluminium normally has no d electrons unlike all other p-block metals. Peculiar metals Slater divides the metals 'fairly definitely, though not perfectly sharply' into the ordinary metals and the peculiar metals, the latter of which verge on the nonmetals. The peculiar metals occur towards the ends of the rows of the periodic table and include 'approximately:' gallium, indium, and thallium; carbon, silicon '(both of which have some metallic properties, though we have previously treated them as nonmetals),' germanium and tin; arsenic, antimony, and bismuth; and selenium '(which is partly metallic)' and tellurium. The ordinary metals have centro-symmetrical crystalline structures whereas the peculiar metals have structures involving directional bonding. More recently, Joshua observed that the peculiar metals have mixed metallic-covalent bonding. Poor metals Farrell and Van Sicien use the term poor metal, for simplicity, 'to denote one with a significant covalent, or directional character.' Hill and Holman observe that, 'The term poor metals is not widely used, but it is a useful description for several metals including tin, lead and bismuth. These metals fall in a triangular block of the periodic table to the right of the transition metals. They are usually low in the activity (electrochemical) series and they have some resemblances to non-metals.' Reid et al. write that 'poor metals' is, '[A]n older term for metallic elements in Groups 13‒15 of