water - Electrolysis of sodium chloride solution

I am trying to understand electrolysis. My question is: when electrolysis is done with a NaCl solution I have learnt that sodium metal is not formed. Why is this?

Answer

Let's look at these two redox couples: $$\ce{Na+ + e- <=> Na} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,E^0(\mathrm{red})=-2.71 V $$ $$\ce{2H2O + 2e- <=> H2 +2OH- }\,\,\,\, E^0(\mathrm{red})=-0.83 V $$ Because it is much easier to reduce water than $\ce{Na+}$ ions, the only product formed at the cathode is hydrogen gas.