The electron configuration for the Mo3+ ion can be determined by first looking at the electron configuration of the neutral molybdenum (Mo) atom. Molybdenum has an atomic number of 42, and its neutral electron configuration is:
Mo: [Kr] 5s2 4d4
When molybdenum loses three electrons to become Mo3+, the electrons are removed first from the outermost orbitals. In this case, the two 5s electrons will be removed first, followed by one of the 4d electrons. Therefore, the electron configuration for Mo3+ is:
Mo3+: [Kr] 4d3
This configuration shows that the Mo3+ ion has three electrons in the 4d subshell, resulting in a stable electron arrangement for the ion.