Final answer:
Iron has 4 unpaired electrons in its 3d subshell in the ground state, leading to a paramagnetic property due to these unpaired electrons.
Step-by-step explanation:
The number of unpaired electrons in the ground state electron configuration for iron (Fe) can be determined from its electron configuration. The atomic number of iron is 26, which corresponds to an electron configuration of [Ar] 4s² 3d⁶. Therefore, in the ground state, iron has 4 unpaired electrons in the 3d subshell, where the 3d6 configuration can be represented as ↑↓ ↑↓ ↑ ↑ ↑ (using arrows to represent the spin of electrons). A 6th electron enters, pairing up with only one of the previously unpaired electrons due to Hund's rule, which states that electrons will fill an empty orbital before they pair up in a given subshell. As a result, iron is paramagnetic, which means it is attracted to a magnetic field because of these unpaired electrons.