Question

An electron is at ground state of the h atom. minimum energy required to excite the h atom into second excited state is

Answer 1

According to Bohr's model of hydrogen atom, energy of an electronic in any shell is given by the equation

E=-13.6÷n2

For 3rd orbit, value of n is 3. Therefore energy of 3rd orbit is -1.51 ev

For ground state, value of n is 1. Therefore energy is -13.6 ev

So the answer to your question is

-1.51-(-13.6) = 12.09 ev

Also for quicker calculations you may prefer to by heart some of the values of energy of electron in different shells.