The metallic sodium disolves in liquid ammonia to form a deep blue coloured solution. The deep blue colour is due to formation of :

A metal M readily forms its sulphate MSO₄, which is water-soluble. It forms its oxide MO which becomes inert on heating. It forms an insoluble hydroxide M(OH)₂ which is soluble in NaOH solution. The M is :

A similarity between optical and geometrical isomerism is that

The functional group, which is found in amino acid is