All of these elements can form compounds in other oxidation states. Aluminium forms some compounds in the +1 state (e.g. see the section in https://en.wikipedia.org/wiki/Aluminium_iodide), as does Zinc (see the section in https://en.wikipedia.org/wiki/Compounds_of_zinc) and Cadmium (e.g. https://en.wikipedia.org/wiki/Cadmium(I)_tetrachloroaluminate). But ...


Paramagnetism is directly proportional to the number of unpaired electrons in an atom or molecule. Looking at the electronic configurations, we see that nitrogen has 3 unpaired electrons, Oxygen 2, Aluminium 1 and Calcium none. Therefore, N>O>Al>Ca in paramagnetic character.

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