Which one is not paramagnetic among the following ? [ at. no. of $$Be = 4,\,Ne = 10,\,As = 33,\,Cl = 17\,$$       ]

Solution :
Paramagnetic character is based upon presence of unpaired electron.
$${}_{17}C{l^ - } = 1{s^2},2{s^2}2{p^6},3{s^2}3p_x^23p_y^23p_z^2$$
In $$C{l^ - }$$ no unpaired electron, so it is in nature diamagnetic.
$${}_4Be = 1{s^2},2{s^1}2p_x^1$$
$${}_{10}N{e^{2 + }} = 1{s^2},2{s^2}2p_x^22p_y^12p_z^1$$
$${}_{33}A{s^ + } = 1{s^2},2{s^2}2{p^6},3{s^2}3{p^6}3{d^{10}},$$       $$4{s^2}4p_x^14p_y^14p_z^0$$
While all others have unpaired electron, so they are paramagnetic in nature.