In metallurgy the term "gangue" is used for :

The reaction of zinc with excess of aqueous alkali, evolves hydrogen gas and gives :

Lithium nitrate and sodium nitrate, when heated separately, respectively, give :

Number of lone pairs of electrons in the central atom of $$\mathrm{SCl}_{2}, \mathrm{O}_{3}, \mathrm{ClF}_{3}$$ and $$\mathrm{SF}_{6}$$, respectively, are :