Group 7: Manganese Family

Group 7 includes Manganese (Mn), Technetium (Tc), Rhenium (Re), and Bohrium (Bh). The last two are very rare on earth. They have terrestrial abundances of about 0.1 ppb. Technetium was formally discovered by Carlo Perrier, Technetium is only available in trace amounts in nature. Group 7 has two naturally occurring transition metals. The other elements in this group are completely synthetic. The Greek term for “artifice” inspired the naming of these organisms. Technetium, rhenium, and Bohrium are all radioactive, although Bohrium and technetium are less radioactive than Ruthenium. They are also not found in nature in large enough quantities to be mine (Guo & Kleppa, 1998).

 

1. Electronic Configuration

The d-orbital configuration of some group 7 elements is half-filled. These elements are called inner transition elements. Many of them lose two or three electrons. However, some of them have half-filled d subshells. General electronic configuration of group 7 is (n-1) ns2 nd5, while the electronic configuration of Group 7 members is as follows (Hiraoka, & Yoshizawa, 2004).

 

Mn [25] 1s2 2s2 2p6 3s2 3p6 4s2 3d5 or [Ar] 4s2 3d5
Tc [43] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d5 or [Kr] 5s2 4d5
Re [75] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d5 or [Xe] 6s2 4f14 5d5
Bh [107] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d5 or [Rn] 7s2 5f14 6d5

 

2. Trend in the physical properties

Elements of this group are non-metallic, nonpolar and have high melting and boiling point, they also show variation in atomic radius and ionization energy (Griffith, 2010). They are used in medicines, lighting, and for sterilization. Halogens share many of the same physical properties as their metal counterparts, but their reactivity and atomic size vary as they move down the group.

 

2.1. Atomic and ionic radii

Atomic and ionic radius of group 7 elements show an irregular change in their radii from manganese to Borhium, while the ionic radius of Bh7+ is unknown (Guo & Kleppa, 1998).

Atomic radius group 5 periodic table />

Figure 1: Atomic radius of Group 7 elements

Ionic radius group 5 periodic table />

Figure 2: Ionic radius of Group 7 elements

 

2.2. Ionization energy

Elements of Group 7 also show irregular behavior in their ionization energy. Rhenium has highest ionization energy among all the member of its group (Hiraoka, & Yoshizawa, 2004).

First ionization energy group 5 periodic table />

Figure 3: First Ionization Energy of the Group 7 elements

 

2.3. Melting and boiling point

Melting and boiling point of Group 7 elements increases from Manganese to Rhenium, while boiling point of Bohrium is lower than the other member of its group and melting point is lower than its previous member (Griffith, 2010).

melting and boiling points group 5 periodic table />

Figure 4: Melting and Boiling Points of the Group 7 elements

 

3. Coordination chemistry of group 7

Coordination compounds of group 7 elements are Mn(phen)(NCS)2, Mn(NCS)2 and Mn(NCSe)2, bis(diazenido)technetium complex tris(l,2-benzenedithiolato)technetium(VI), [cis Re(CO)4(Pi-Pr3)(ClCH2Cl)][BArF] and so on . Ions of Chromium-54 form a Bohrium-Chromium complex. Manganese oxides are mainly monitored by the rate of Oxygen diffusion. This is done by the presence of a dative bond that is formed between the central metal atom and the ions. The cohesion spherical is another name for this concept. The sphere has a net charge that is associated with the ions.

Coordination complexes of Molybdenum and Chromium />

Figure 5: Coordination complexes of Manganese and Technetium

 

4. Uses of group 6 elements

These elements are important because they are used in a variety of applications. These elements have various uses and are involved in coordination chemistry. Technetium is now used as a radioactive tracer. The element is also used to image internal organs. Complexes with a transition metal as the central atom are commonly used in the dye and pigment industries (Hiraoka, & Yoshizawa, 2004; Griffith, 2010)

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References

1. Griffith, W. P. (2010). The group VIII platinum-group metals and the Periodic Table. Foundations of Chemistry, 12(1), 17-25.
2. Guo, Q., & Kleppa, O. J. (1998). Standard enthalpies of formation of some alloys formed between group IV elements and group VIII elements, determined by high-temperature direct synthesis calorimetry: II. Alloys of (Ti, Zr, Hf) with (Co, Ni). Journal of alloys and compounds, 269(1-2), 181-186.
3. Hiraoka, Y., Ogusu, T., & Yoshizawa, N. (2004). Decrease of yield strength in Molybdenum by adding small amounts of Group VIII elements. Journal of alloys and compounds, 381(1-2), 192-196.