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The element with atomic number 111 might belong to which of the following groups?
A.Chromium
B.Scandium
C.Copper
D.Titanium

Answer
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Hint: The noble gas nearest to the element with atomic number 111 is Radon86. Now we can write the electronic configuration of the element, through which the valence shell configuration of the element can be found. The elements of the same group have similar valence shell configuration.

Complete step by step answer:
As the noble gas nearest to the given element is Radon having atomic number 86, we deduce that the first 86 electrons out of 111 are configured in the atomic orbitals in the same way as Radon.
Electronic configuration of Radon is,
Rn=1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p6
This means the next electron will start filling from the 7s orbital. So, the rest 25 electrons will occupy the successive orbitals as follows,
[Rn]7s25f146d9 (expected electronic configuration)
As we can see the last electron lies in the 6d subshell and the valence shell configuration is d9.
The elements given above have electronic configuration as follows,
24Cr=[Ar]4s13d5
21Sc=[Ar]4s23d1
29Cu=[Ar]4s13d10
22Ti=[Ar]4s23d2
The expected electronic configuration of Cu is 29Cu=[Ar]4s23d9, but due to higher stability associated with fully filled orbitals its configuration changes from d9 to d10 by the transfer of 1 electron from 4s subshell to 3d subshell.
As we know the elements of the same group have the same general electronic configuration, and we can see that both Cu and the element with atomic number 111, have general valence shell electron of, ns2(n1)d9.
Therefore, the element with atomic number 111 lies in the same group as Copper, that is, group 11.

Hence option C is correct.

Note:
Due to the same general electronic configuration of the elements that lie in the same group, the number of valence electrons are same and they have similar chemical properties too. For example, the elements of group 1 are called the alkali metals and they have general electronic configuration of ns1. They are very reactive metals and form monovalent ionic species. They have the largest atomic radii in their respective periods.