Question

what is the first excited state of H atom?

Answer 1

If the question is asking what is the "energy" of the first excited state then you can find that answer by using the the energy eigenvalue equation \[E_{n}=-13.6 eV/n^{2}\] where \[n=1,2,3...\]
where for the ground state \[n =1\] and for the the first excited state \[n=2 \] and so on.

Answer 2

thank you but is H atom which in excited state is stable H atom?

Answer 3

I don't get what you mean? Are you asking whether the equation I gave is for the hydrogen atom that everyone knows and loves? :)