Final answer:
The electron configuration for Nb³⁺ is [Kr]4d², with three electrons removed from the 5s and 4d orbitals of the neutral niobium atom.
Step-by-step explanation:
The electron configuration for Nb³⁺ (niobium with a 3+ charge) is determined by first writing the electron configuration for the neutral Nb atom and then removing three electrons because of the positive charge. The neutral Nb atom, with an atomic number of 41, would have the configuration [Kr]5s²4d⁴.
When three electrons are removed to account for the positive charge of Nb³⁺, they are taken from the 5s and 4d orbitals. The electron configuration for Nb³⁺ thus becomes [Kr]4d², which means two valence electrons are present in the 4d orbital after the two 5s electrons have been removed. This configuration follows the common pattern where s-orbital electrons are removed before d-orbital electrons in transition metals when forming cations.