To determine whether an atom or ion is paramagnetic, we need to look at its electronic configuration and check for unpaired electrons. Paramagnetic substances have one or more unpaired electrons, which give rise to magnetic properties.
A. Cl (Chlorine): The electronic configuration of Cl is [Ne] 3s² 3p⁵. It has one unpaired electron in the 3p subshell. Thus, Cl is paramagnetic.
B. Ca²⁺ (Calcium ion): The electronic configuration of Ca is [Ar] 4s², and when it loses two electrons to form Ca²⁺, its configuration becomes [Ar]. There are no unpaired electrons in Ca²⁺, making it diamagnetic.
C. Ca (Calcium): As mentioned, the electronic configuration of Ca is [Ar] 4s². There are no unpaired electrons here either, so Ca is also diamagnetic.
D. Ar (Argon): The electronic configuration of Ar is [Ne] 3s² 3p⁶. All electrons are paired in argon, which makes it diamagnetic.
E. Si (Silicon): The electronic configuration of Si is [Ne] 3s² 3p². Silicon has two unpaired electrons in the 3p subshell, so Si is paramagnetic.
In summary, the elements that possess paramagnetic properties from the given options are Cl (Chlorine) and Si (Silicon), while Ca²⁺, Ca, and Ar are diamagnetic.