ABSTRACT
The Group 13 consists of ve elements: boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (TI). These elements have three electrons in their outer energy levels, thus their valence is mainly +3 (Table 18.1). Geochemical and biochemical properties, as well as the abundance in the biosphere, of all these elements are highly divergent. Their common characteristic is a strong af nity for oxygen. Among them, only B is metalloid (nonmetal) and plays a signi cant role in plants. Aluminum, being one of the basic constituents of the lithosphere, reveals amphoteric properties. Three other trace metals (Ga, In, and Tl) are widely, but at low concentrations, distributed in the lithosphere and biosphere.
