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].

List of Post-Transition Metals
Aluminium	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 as transition metals), and for germanium and antimony (otherwise considered as metalloids) ^[1].

Properties and Characteristics of Post-Transition Metals

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 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, ionisation 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 application in semiconductors and fuel cells ^{[1, 2]}. Lead is used in making batteries, among other things.

Interesting Facts

• Aluminium 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 wasdiscovered to be mildly radioactive.

References:

1. https://www.ducksters.com/science/chemistry/post-transition_metals.php
2. http://www.miningoilgasjobs.com.au/mining/all-you-need-to-know-about-the-mining—metals-sec/quick-facts-about-post-transition-metals.aspx
3. https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/Post-transition_metal.html
4. https://posttransitionmetals.weebly.com/properties-of-the-post-transition-metals.html
5. https://prezi.com/c8vo6gdp78-n/post-transition-metals/
6. https://schooledbyscience.com/everyday-uses-of-basic-metals/