Introduction:
The magnetic properties of molecules depend on the presence of unpaired electrons. Transition metal compounds often exhibit paramagnetic or diamagnetic behavior due to the presence or absence of unpaired electrons in their d orbitals. In this context, we will discuss the magnetic properties of TiCl2 and TiO2.

TiCl2:
TiCl2 is a compound of titanium and chlorine. Titanium has an atomic number of 22, and its electronic configuration is [Ar] 3d^24s^2. In TiCl2, titanium is in its +2 oxidation state, which means it has lost two electrons. The electronic configuration of Ti2+ is [Ar] 3d^2.

Paramagnetism:
Paramagnetic substances are attracted to an external magnetic field due to the presence of unpaired electrons. TiCl2 is paramagnetic because titanium in its +2 oxidation state has two unpaired electrons in its d orbitals (3d^2). The presence of unpaired electrons allows the compound to align its magnetic moments with the external magnetic field, resulting in attraction.

TiO2:
TiO2 is a compound of titanium and oxygen. Titanium in TiO2 is in its +4 oxidation state, which means it has lost four electrons. The electronic configuration of Ti4+ is [Ar] 3d^0.

Diamagnetism:
Diamagnetic substances are repelled by an external magnetic field due to the absence of unpaired electrons. TiO2 is diamagnetic because titanium in its +4 oxidation state has all its d orbitals fully filled (3d^0). The absence of unpaired electrons means that there are no magnetic moments to align with an external magnetic field, resulting in repulsion.

Conclusion:
In summary, TiCl2 is paramagnetic because titanium in its +2 oxidation state has two unpaired electrons in its d orbitals. On the other hand, TiO2 is diamagnetic because titanium in its +4 oxidation state has all its d orbitals fully filled, with no unpaired electrons. The presence or absence of unpaired electrons in the d orbitals of transition metal compounds determines their magnetic properties.