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Post-Transition Metals

Definition : What are Post-Transition Metals

The post-transition elements in the periodic table are a group of elements located between the transition metals (to the right) and metalloids (to the left). Due to their properties, they are also called ‘other’ or ‘poor’ metals [1].

Location of the Post-Transition Metals in the Periodic Table

Although there are some conflicting theories, generally the post-transition metals include elements from groups 13-15 [1,2].

Post-Transition Metals on the Periodic Table

List of Post-Transition Metals

Aluminum Al
Gallium Ga
Indium In
Tin Sn
Thallium Tl
Lead Pb
Bismuth Bi

The elements 113-116 on the periodic table, i.e. nihonium (Nh), flerovium (Fl), moscovium (Mc), and livermorium (Lv), are considered to possibly belong to the post-transition metal family, though it is yet to be confirmed due to some unknown properties of the elements [6].

Polonium is sometimes also included in the list of post-transition metals. The same may be done for zinc, cadmium, and mercury (otherwise considered transition metals) and for germanium and antimony (otherwise considered metalloids) [1].

Properties and Characteristics of Post-Transition Metals

Post-Transition Metal Example Bismuth

Physical Properties

  • Soft or brittle, poor mechanical strength [3]
  • Melting points lower than transition metals
  • Boiling points are also usually lower than transition metals [3]
  • Covalent or directional bonding is shown by crystalline structures [4]
  • High density [5]

Chemical Properties

  • Tendency to form covalent bonds [3]
  • Acid-Base amphoterism
  • Can form half-metallic compounds [5]

Periodic Trends of Post-Transition Metals

Generally, atomic radii decrease, and ionization energies increase. As a result, fewer electrons are available for metallic bonding, and so ions are smaller, more polarising, and tend to form covalent bonds. Hence they show lesser metallic nature [3].

Uses of Post-Transition Metals

Different elements in this family have different uses. Aluminium and Tin are respectively used for making utensils in electronics, as well as for soldering and plating steel [5]. Bismuth is used to make Pepto-Bismol, a drug used to soothe upset stomachs [1,5]. Indium is used for electronics, for example, making touch screens and flat panel displays, while Gallium has applications in semiconductors and fuel cells [1, 2]. Lead is used in making batteries, among other things.

Interesting Facts

  • Aluminum is the most abundant post-transition metal and the third most abundant element on Earth [1].
  • The post-transition metal bismuth was considered to be the heaviest stable element until recently, before it was discovered to be mildly radioactive.