Group 13 of the Periodic Table
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Group 13 is the 13th group of the periodic table, consisting of elements whose outer electron shells contain boron (B), aluminium (Al), gallium (Ga), indium (In), and thallium (Tl). Nihonium (Nh), a synthetic element with very short half-life, is also included in this group. The group is named after boron, its lightest element.
The elements of this group share an outer electron configuration with three electrons (ns² np¹). This is why they typically form compounds involving three electrons, such as BF₃ and Al₂O₃, with an oxidation state of +3 being common.
General properties
Boron is a metalloid—not a true metal; it conducts heat and electricity poorly and is extremely hard. The other elements in the group are metals that are soft and shiny at room temperature compared to boron. Aluminium is the most abundant metal in the Earth's crust, while gallium, indium, and thallium are rare.
Chemistry and oxidation states
Moving down the group, the +1 oxidation state becomes more stable. Thallium commonly exists as Tl(+1), whereas boron and aluminium favour +3. Boron uniquely forms many hydride compounds (boranes) with electron-deficient bonding, distinct from the chemistry of the metals in the group.
Applications
Aluminium is used in aerospace, construction, and food packaging because of its low density and corrosion resistance. Boron compounds are employed in heat-resistant glass and detergents. Gallium (particularly gallium arsenide and gallium nitride) and indium (indium tin oxide for displays) are important to the electronics industry. Thallium and its compounds are highly toxic, restricting their use.