Group 6: Chromium Family

Group 6 members include Chromium, Molybdenum, Tungsten and Seaborgium. These elements form anions with a -2 charge. Tungsten is found in rubies, and has been identified in analogous roles in enzymes from some archea. These elements are not as reactive as the metals in Group 1. A few of these elements are synthesized and artificially produced. The elements in consideration have comparable biochemical and physiological characteristics. They may be discovered at the middle of the periodic chart, throughout the shape of small columns. These elements form stable compounds in two or more formal oxidation states (Liu & Lin, 2018).

 

1. Electronic Configuration

General electronic configuration of Group 6 is (n-1) ns1 nd5, while the electronic configuration of Group 6 members is as follows (Wong & Bent, 2010).

 

Cr   [24] 1s2 2s2 2p6 3s2 3p6 4s1 3d5 or [Ar] 4s1 3d5
Mo [42] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d5 or [Kr] 5s1 4d5  
W   [74] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s1 4f14 5d5 or [Xe] 6s1 4f14 5d5

Sg  [106] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s1 5f14 6d5 or [Rn] 7s1 5f14 6d5

 

2. Trend in the physical properties

Their properties are mostly similar to those of the metals in Group 1. However, they differ in their melting points and boiling points. In contrast to Groups 1 metals, those in Period 6 possess lower molten as well as boiled ranges. They are also ductile, malleable, and have low density. They are also good conductors of heat (Xiao, et al., 2012).

 

2.1. Atomic and ionic radii

Atomic and ionic radius of group 6 elements increase from Chromium to Tungsten due to increase in atomic number with the exception of Seaborgium which has smaller size than the other member of its group while ionic radius of Seaborgium ion is unknown (Liu & Lin, 2018).

Atomic radius group 5 periodic table

Figure 1: Atomic radius of Group 6 elements

Ionic radius group 5 periodic table

Figure 2: Ionic radius of Group 6 elements

 

2.2. Ionization energy

Ionization energy of group 6 elements increase from Chromium to Tungsten in group with exception of seagorbium which has lower value of ionization energy than Tungsten (Wong & Bent, 2010).

First ionization energy group 5 periodic table

Figure 3: First Ionization Energy of the Group 6 elements

 

2.3. Melting and boiling point

From Chromium to Tungsten in group 6, melting and boiling point increase continuously while melting and boiling point of Seaborgium is unknown (Xiao, et al., 2012).

melting and boiling points group 5 periodic table

Figure 4: Melting and Boiling Points of the Group 6 elements

 

3. Coordination chemistry of group 6

Elements of group 6 can form coordination compounds. These compounds contain a metal ion bonded to anions and/or a Lewis base donor atom. They involve a central metal ion bonded to a ligand. This ion may be bonded to a finite number of ligands. The ligands contain electrons that can be shared with the metal. The composition of the complex ion and the charge of the ligand determine the color of the compound.

Coordination complexes of Molybdenum and Chromium

Figure 5: Coordination complexes of Molybdenum and Chromium

 

4. Uses of group 6 elements

These elements are known to have significant biological roles in various living organisms. Multiple everyday applications exist for them. Some of the most common uses of these elements include chroming metals and alloys, as well as the manufacture of polymers and other metal alloys. Chromium is used for staining glass these elements are also used in the manufacture of batteries. Lithium batteries power most of today’s digital devices. Coordination complexes of this group 6 elements are used as catalysts in many industrial applications. They are also found in hemoglobin and other biomolecules. Other uses of group 6 elements include the manufacture of batteries, as well as inks and rubbers. Some of these elements are used in manufacturing aircraft parts and oil pipelines. These metals are also used structurally. Metals are used in electrical technology and are used in coinage. They are also used in making high-temperature steels (Xiao, et al., 2012; Liu & Lin, 2018).

You want to know about all the Groups of the Periodic Table?

 

References

1. Liu, D., Lin, X., & Tománek, D. (2018). Microscopic mechanism of the helix-to-layer transformation in elemental group VI solids. Nano Letters, 18(8), 4908-4913.
2. Kachian, J. S., Wong, K. T., & Bent, S. F. (2010). Periodic trends in organic functionalization of group IV semiconductor surfaces. Accounts of chemical research, 43(2), 346-355.
3. Xiao, D., Liu, G. B., Feng, W., Xu, X., & Yao, W. (2012). Coupled spin and valley physics in monolayers of MoS 2 and other group-VI dichalcogenides. Physical review letters, 108(19), 196802.