Which of the following transition metals is not attracted to external magnetic field?

Analyze the question: It asks which metal is not attracted to an external magnetic field. That depends on whether the metal has unpaired electrons.

Concept:

• Paramagnetic substances have unpaired electrons and are weakly attracted to a magnetic field.
• Ferromagnetic substances (Fe, Co, Ni) are strongly attracted.
• Diamagnetic substances have all electrons paired and are weakly repelled by a magnetic field. So they are not attracted.

Solution: check the electron configurations

• Cu (Z = 29): [Ar] 3d¹⁰ 4s¹. The 4s electron is unpaired, so Cu is paramagnetic. Bulk copper metal is in fact very weakly diamagnetic overall, but at WASSCE level it is treated as having an unpaired electron.
• Fe (Z = 26): [Ar] 3d⁶ 4s². It has 4 unpaired electrons and is ferromagnetic, so it is strongly attracted.
• Ti (Z = 22): [Ar] 3d² 4s². It has 2 unpaired electrons, so it is paramagnetic.
• Zn (Z = 30): [Ar] 3d¹⁰ 4s². All electrons are paired, so Zn is diamagnetic. It is not attracted to a magnetic field (it is slightly repelled).

Zn is also often noted as not a "true" transition metal, because its d-orbital is completely filled in both the atom and its ion (Zn²⁺, 3d¹⁰). That is why it lacks the typical transition-metal properties, including paramagnetism.

Answer: The metal with no unpaired electrons is Zn, so it is not attracted to a magnetic field.

Tip: For magnetism questions, write the d-electron configuration and count the unpaired electrons. A full 3d¹⁰ with a full 4s², as in Zn, means diamagnetic and not attracted. Remember that Fe, Co and Ni are the strongly magnetic ones.