Are the following ions diamagnetic or paramagnetic: a) Cr3+ b) Ca2+ c) Na+ d) Fe3+?

To determine whether the given ions are diamagnetic or paramagnetic, we need to consider their electron configurations and whether they have unpaired electrons.

1. Cr³⁺: Chromium (Cr) has an atomic number of 24. The electron configuration of neutral chromium is [Ar] 3d⁵ 4s¹. When it loses three electrons to form Cr³⁺, the configuration becomes [Ar] 3d³. Since there are three unpaired electrons in the 3d subshell, Cr³⁺ is paramagnetic.
2. Ca²⁺: Calcium (Ca) has an atomic number of 20. The electron configuration of neutral calcium is [Ar] 4s². When it loses two electrons to form Ca²⁺, the configuration becomes [Ar]. With no unpaired electrons, Ca²⁺ is diamagnetic.
3. Na⁺: Sodium (Na) has an atomic number of 11. The electron configuration of neutral sodium is [Ne] 3s¹. When it loses one electron to form Na⁺, the configuration becomes [Ne]. Again, there are no unpaired electrons, so Na⁺ is diamagnetic.
4. Fe³⁺: Iron (Fe) has an atomic number of 26. The electron configuration of neutral iron is [Ar] 3d⁶ 4s². When it loses three electrons to form Fe³⁺, the configuration is [Ar] 3d⁵. With five unpaired electrons in the 3d subshell, Fe³⁺ is paramagnetic.

In summary:

• Cr³⁺: Paramagnetic
• Ca²⁺: Diamagnetic
• Na⁺: Diamagnetic
• Fe³⁺: Paramagnetic