Which one of the following complexes shows optical isomerism?
(en = ethylenediamine)

Which of the following compounds is metallic and ferromagnetic ?

A stream of electrons from a heated filament was passed between two charged plates kept at a potential difference V esu. If e and m are charge and mass of an electron, respectively, then the value of h / $$\lambda $$ (where $$\lambda $$ is wavelength associated with electron wave) is given by :

The species in which the $\mathrm{N}$ atom is in a state of $s p$ hybridization is :