Final answer:
Nickel (Ni) is the element that is paramagnetic among the options given because it has unpaired electrons in its 3d subshell, which gives it a magnetic dipole moment. Option number 3 is correct.
Step-by-step explanation:
In order to determine which of the given elements (Mg, Ca, Ni, Zn) is paramagnetic, we have to look at their electron configurations according to the Aufbau principle, which establishes that electrons fill up atomic orbitals starting from the lowest energy level to the highest.
Elements that have unpaired electrons in their orbitals display paramagnetic properties, as they are attracted by a magnetic field. Paramagnetism occurs because these unpaired electrons create a magnetic dipole moment.
The electron configuration for Mg (Magnesium) ends in 3s2, for Ca (Calcium) it ends in 4s2, for Ni (Nickel) it ends in 4s23d8, and for Zn (Zinc) it ends in 4s23d10. Here, we can see that Mg and Ca each have filled subshells with no unpaired electrons, while Ni has unpaired electrons in the 3d subshell, making it paramagnetic. Zn has a filled 3d subshell, resulting in no unpaired electrons, making it diamagnetic.
Thus, Ni (Nickel) is the element that is paramagnetic as it does not follow the aufbau principle filling order and has unpaired electrons.