Final answer:
Osmium in its ion form Os³⁺ has 5 electrons in its valence d orbitals, after it loses the s orbital electrons first when it forms a cation.
Step-by-step explanation:
The student is asking about the number of electrons in the valence d orbitals of the transition-metal ion Os3+. Osmium (Os) is a transition metal, and in its neutral state, it would have an electron configuration that ends with 5d6 6s2. When forming the Os³⁺ ion, it loses electrons to achieve a positive charge.
According to the electron removal process for transition metals, the s orbital electrons are lost first before the d orbital electrons.
Therefore, for Os³⁺, three electrons are lost from the 6s and the first part of the 5d orbitals, leading to an electron configuration ending in 5d5. Consequently, there are 5 electrons in the valence d orbitals of Os³⁺.