A neutron collies head-on with a stationary hydrogen atom in ground state. Which of the following statements is/are correct ?

Lithium and hydrogen atom are in their second excited state. Which of the following statement/s is/are correct ?

The radius of hydrogen atom, in the ground state is of the order of

The radius of hydrogen atom, in its ground state, is of the order of

The ionization energy of Hydrogen atom in its ground state is……

The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true?