Question

Transition metal has the general electronic configuration?
A.${\text{n}}{{\text{s}}^2}{\text{n}}{{\text{d}}^{1 - 10}}$
B.${\text{n}}{{\text{s}}^2}{\text{n}}{{\text{p}}^1}\left( {{\text{n}} - 1} \right){{\text{d}}^{1 - 10}}$
C.${\text{n}}{{\text{s}}^{1 - 2}}\left( {{\text{n}} - 1} \right){{\text{d}}^{1 - 10}}$
D.${\text{n}}{{\text{s}}^2}{\text{n}}{{\text{p}}^6}\left( {{\text{n}} - 1} \right){{\text{d}}^{1 - 10}}$

Answer 1

Electron from s subshell jumps to d subshell in order to increase its stability. The d subshell can have a maximum ten electrons in it. If n is the valence shell then $\left( {{\text{n}} - 1} \right)$ will be the penultimate shell.

Complete step by step answer:
- Each orbital in an atom is designated by a set of three quantum numbers and each electron is designated by a set of four quantum numbers. Principal quantum number represents the name, size and energy of the shell to which the electron belongs. It is represented by n. Azimuthal quantum number represents the shape of the subshell and orbital. It is represented by l. Magnetic quantum number represents the orientation of the orbital. It is represented by m. Spin quantum number represents the direction of electron spin around its own axis. It is represented by s.
- In modern periodic tables, elements of a group have the same outer shell general electronic configuration. Transition metals are the elements belonging to the d block. In modern periodic tables, transition metals are from group 3 to 12 and from period 4 to period 6. The general electronic configuration of transition metal is ${\text{n}}{{\text{s}}^{1 - 2}}\left( {{\text{n}} - 1} \right){{\text{d}}^{1 - 10}}$.
- Zinc, Cadmium and mercury belong to the d block but they are not transition elements as they do not possess unpaired electrons in their d subshell. As half filled and fully filled orbitals are more stable, sometimes in order to gain more stability. In d block, an electron from s subshell jumps to d subshell to make it half or full filled. For example electronic configuration of Chromium is ${\text{4}}{{\text{s}}^1}{\text{3}}{{\text{d}}^5}$ and for copper is ${\text{4}}{{\text{s}}^1}{\text{3}}{{\text{d}}^{10}}$. Also d subshell has five orbits to which it can have a maximum ten electrons. Thus ${\text{n}}{{\text{s}}^{1 - 2}}\left( {{\text{n}} - 1} \right){{\text{d}}^{1 - 10}}$ is the general electronic configuration of transition elements.

Thus, the correct option is C.

Note:
Aufbau principle gives a sequence in which various subshells are filled up depending on the relative order of the energies of various subshells. Pauli stated that two electrons in an atom can never have all four quantum numbers the same. Hund rule explains that a subshell pairing of electrons will not start until and unless all the orbitals of that subshell will get one electron each with the same spin.