The periodic table arranges all known elements based on their atomic number and recurring chemical properties. This structure uses vertical columns, known as groups, and horizontal rows called periods. Group 13 is the first group in the p-block, situated between the alkaline earth metals (Group 2) and the carbon group (Group 14). The position of elements within these groups dictates their common chemical behaviors.
The Group 13 Name and Member Elements
Group 13 is most frequently referred to as the Boron Group, named after the element at the top of the column. The six members are Boron (B), Aluminum (Al), Gallium (Ga), Indium (In), Thallium (Tl), and the synthetic element Nihonium (Nh). These elements are also collectively called the Triels, referencing the three valence electrons they possess. Nihonium is a highly unstable, artificially created element produced in particle accelerators and is not found in nature.
Fundamental Chemical Characteristics
The unifying chemical characteristic for all Group 13 elements is their valence electron configuration, consistently written as \(ns^2 np^1\). This means each atom has three valence electrons. The loss of all three electrons results in the group’s most common oxidation state of +3.
Having only three valence electrons leaves the neutral compounds of these elements electron deficient. This lack of a full octet means Group 13 compounds often act as Lewis acids, accepting electron pairs in chemical reactions. While the elements typically form compounds with a +3 oxidation state, Boron’s small size causes it to favor stable covalent bonds. In contrast, the larger metallic elements lower down the group are more likely to form ionic compounds.
Transitioning Properties Down the Group
A shift in properties occurs down Group 13, driven by increasing atomic size. Boron is unique, classified as a metalloid, and its small atomic radius forces it into almost exclusively covalent bonding. Aluminum is the first true metal in the group and is notable for its amphoteric nature, reacting with both acids and bases. The metallic character continues to increase from Gallium, through Indium, and down to Thallium.
The heaviest elements, especially Thallium, display the inert pair effect. This effect is caused by the poor shielding of the nucleus by intervening d and f electrons, which holds the two \(ns^2\) valence electrons tightly. This increased attraction makes the \(ns^2\) electron pair reluctant to participate in bonding. Consequently, Thallium often exhibits a stable +1 oxidation state, where only the single p-electron is lost, in addition to the characteristic +3 state.
Key Applications of Group 13 Elements
The unique properties of Group 13 elements lead to diverse industrial applications. Aluminum is the most commercially significant member, prized for its low density and high strength-to-weight ratio, making it a primary material for aircraft and construction. The metal naturally forms a thin, protective layer of aluminum oxide, providing exceptional resistance to corrosion.
Boron, often used as borosilicate glass, is found in laboratory glassware and cookware due to its resistance to thermal shock. Boron compounds also play a role in nuclear applications, such as reactor control rods, because the isotope boron-10 is an excellent neutron absorber. Gallium is valuable in the electronics industry, used in compounds like gallium arsenide and gallium nitride, which are essential semiconductors in light-emitting diodes (LEDs) and high-speed integrated circuits.