Group 12: Zinc Family

Group 12 includes Zinc (Zn), Cadmium (Cd), Mercury (Hg), and Copernicium (Cn). Mercury is a natural element and it is a toxic liquid metal at room temperature. Mercury’s chemistry is different from that of zinc and cadmium. Zinc is the most reactive metal in Group 12. It has two valence electrons, and it reacts easily with oxygen. The zinc compounds have a metallic character (Houck, et al., 2018).

 

1. Electronic Configuration

General electronic configuration of group 12 is (n-1) ns2 nd10, while the electronic configuration of group 12 members is as follows (Frontera, 2020).

 

Zn [30] 1s2, 2s2, 2p6, 3s2, 3p6, 4s2 3d10 or [Ar] 4s2 3d10

Cd [48] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 or [Kr] 5s2 4d10

Hg [80] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 or [Xe] 6s2 4f14 5d10

Cn [112] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 or [Rn] 7s2 5f14 6d10

 

2. Trend in the physical properties

Elements of this group show following trend in their physical properties (Shukla, Arora & Srivastava, 2022).

 

2.1. Atomic and ionic radii

Atomic and ionic radii of Group 12 elements increases from Zn to Hg with the exception of Cn whose atomic radii is smaller than Hg while ionic radius of Cn is unknown (Houck, et al., 2018).

Atomic radius group 5 periodic table

Figure 1: Atomic radius of Group 12 elements

Ionic radius group 5 periodic table

Figure 2: Ionic radius of Group 12 elements

 

2.2. Ionization energy

Ionization energy of group 12 elements increases from zinc to copernicium with exception of cadium which is lower than previous element (Frontera, 2020).
Ionization energy of group 12 elements in kilo joule per mole.

 

First ionization energy group 5 periodic table

Figure 3: First Ionization Energy of the Group 12 elements

 

2.3. Melting and boiling point

Melting and boiling point of Group 12 elements decreases from zinc to mercury while melting and boiling point of copernicium is unknown (Shukla, Arora & Srivastava, 2022).

melting and boiling points group 5 periodic table

Figure 4: Melting and Boiling Points of the Group 12 elements

 

3. Coordination chemistry of Group 12

• Several recent research papers have addressed the relevance of zinc in structural proteins. These studies show that zinc coordinates with proteins via a conserved structural domain. Zn (II) coordinates with proteins through cysteine sulfhydryl groups and histidine imidazole rings.
• Zn (II) is an essential component of the catalytic sites of enzyme structural proteins. These proteins contain zinc finger motif. Zinc is also involved in the modulation of various ionotropic receptor channels.
• Several coordination complexes of cadmium have been studied in the laboratory. These complexes exhibit different mechanisms of action, and may have a potential for use in treatment of some diseases.
• Cysteine is a ligand for Cadmium(II) ions. In addition, Cadmium(II) is highly oxidative, which makes the coordination of it with cysteine more efficient.

 

4. Uses of Group 12 elements

Following are the important uses of group 12 elements (Frontera, 2020; Shukla, Arora & Srivastava, 2022)
• Zinc is used in making several alloys. Its good abrasive resistance and room temperature mechanical properties make it suitable for various industries .Besides its use as a metal, zinc is also used in zinc alloys and zinc oxide.
• Despite being one of the most toxic metals in the environment, cadmium is used in many different industrial processes. These include metal coatings, plating, batteries, and chemical reactions.
• One of the primary uses of cadmium in the United States is in rechargeable nickel-cadmium batteries. These batteries power portable computers and cell phones. They are also used in photodetectors and fluorescence microscopes.
• Mercury has found applications in medicine, science, agriculture, and technology.
• Among the many uses of mercury, one of the most common is in thermometers and manometers. Mercury’s solubility is useful for determining the concentration of metals in liquids.
• Mercury is a heavy metal, which makes it a potential hazard to humans. It is poisonous and can cause chronic poisoning. As a result, uses of mercury have been restricted. In the United States, it is now prohibited in paints and pesticides

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Conclusion

Despite being considered transition metals, the group 12 elements have very different properties and behaviors. Although they form compounds with oxidation states ranging from +2 to +4, their electronic configurations are more similar to those of alkaline earth metals. The most common oxidation state for all group 12 elements is +2. However, the oxidation states vary, and many of the group’s compounds have d10 electronic configurations. This makes the group very malleable, and its electrons can fill partially with elements from group 11. Unlike the other transition metals, group 12 elements are divalent, meaning they have one valence electron and a tightly bound ns electron.

 

References

1. Roccanova, R., Houck, M., Yangui, A., Han, D., Shi, H., Wu, Y., … & Saparov, B. (2018). Broadband Emission in Hybrid Organic–Inorganic Halides of Group 12 Metals. ACS omega, 3(12), 18791-18802.
2. Bauzá, A., Alkorta, I., Elguero, J., Mooibroek, T. J., & Frontera, A. (2020). Spodium bonds: noncovalent interactions involving group 12 elements. Angewandte Chemie International Edition, 59(40), 17482-17487.
3. Shukla, N., Kaur, H., Arora, B., & Srivastava, R. (2022). Two-dipole and three-dipole interaction coefficients of group XII elements. Physica B: Condensed Matter, 624, 413422.