An element A burns with golden flame in air. It reacts with another element B, atomic number 17 to give a product C. An aqueous solution of product C on electrolysis gives a compound D and liberates hydrogen. Identify A, B, C and D. Also write down the equations for the reactions involved. 

Explanation

Element A is sodium that burns with golden flame. Element B is chlorine. Its atomic number is 17. Product C is sodium chloride. Compound d is sodium hydroxide. When sodium reacts with chlorine, it gives sodium chloride.
`Na + Cl rarr NaCl`
Electrolysis of sodium shloride gives sodium hydroxie.
`2NaCl + 2H_(2)O rarr 2NaOH + Cl_(2) + H_(2)`