Answer: The correct answer is Option B.
Explanation:
Valence electrons are defined as the electrons which are present in outermost shell of an atom. This is determined by the electronic configuration of an element.
For the given options:
Option A: Vanadium (V)
The atomic number of this atom is 23 and number of electrons that are present are 23. The electronic configuration of vanadium is:
[tex]V:[Ar]3d^34s^2[/tex]
This element does not have 3 electrons in 4d-subshell.
Option B: Niobium (Nb)
The atomic number of this atom is 41 and number of electrons that are present are 41. The electronic configuration of niobium is:
[tex]Nb:[Kr]4d^35s^2[/tex]
This element have 3 electrons in 4d-subshell.
Option C: Copper (Cu)
The atomic number of this atom is 29 and number of electrons that are present are 29. The electronic configuration of copper is:
[tex]Cu:[Ar]3d^{10}4s^1[/tex]
This element does not have 3 electrons in 4d-subshell.
Option D: Thallium (Tl)
The atomic number of this atom is 81 and number of electrons that are present are 81. The electronic configuration of thallium is:
[tex]Tl:[Xe]4f^{14}5d^{10}6s^26p^1[/tex]
This element does not have 3 electrons in 4d-subshell.
Hence, the correct answer is Option B.
