Which of these hydrated cations are colorless: \(\mathrm{Fe}^{2+}(a q), \mathrm{Zn}^{2+}(a q), \mathrm{Cu}^{+}(a q), \mathrm{Cu}^{2+}(a q), \mathrm{V}^{5+}(a q)\) \(\mathrm{Ca}^{2+}(a q), \mathrm{Co}^{2+}(a q), \mathrm{Sc}^{3+}(a q), \mathrm{Pb}^{2+}(a q) ?\) Explain your choice.

Look at each of the cations and determine whether they have unfilled d or f orbitals. For s- and p-block elements, look for whether they have finished their last electron at s or p. For d-block elements, look at whether they have partially filled d orbitals. Here is the list: 1. \( \mathrm{Fe}^{2+}(a q) \) - Iron(II), d-block metal, has unfilled d orbitals.2. \( \mathrm{Zn}^{2+}(a q) \) - Zinc, d-block metal, has no unfilled d orbitals in its 3d10 configuration.3. \( \mathrm{Cu}^{+}(a q) \) - Copper(I), d-block metal, has no unfilled d orbitals in its 3d10 configuration.4. \( \mathrm{Cu}^{2+}(a q) \) - Copper(II), d-block metal, has no unfilled d orbitals in its 3d9 configuration.5. \( \mathrm{V}^{5+}(a q) \) - Vanadium(V), d-block metal, has unfilled d orbitals.6. \( \mathrm{Ca}^{2+}(a q) \) - Calcium, s-block element, has no d or f orbitals in its 4s2 configuration. 7. \( \mathrm{Co}^{2+}(a q) \) - Cobalt, d-block metal, has unfilled d orbitals.8. \( \mathrm{Sc}^{3+}(a q) \) - Scandium, d-block metal, has no unfilled d orbitals in its 3d1 configuration.9. \( \mathrm{Pb}^{2+}(a q) \) - Lead, p-block element, has no d or f orbitals in its 6s2 configuration.

Identify the cations that have no unfilled d or f orbitals. These cations are colorless because they don't have the necessary conditions for absorption or emission of light. From the previous step, these include the cations: \( \mathrm{Zn}^{2+}(a q) \), \( \mathrm{Cu}^{+}(a q) \), \( \mathrm{Cu}^{2+}(a q) \), \( \mathrm{Ca}^{2+}(a q) \), \( \mathrm{Sc}^{3+}(a q) \), and \( \mathrm{Pb}^{2+}(a q) \).