Which electronic level would allow the hydrogen atom to absorb a photon but not to emit a photon?

The increasing order (lowest first) for the values of e/m (charges/mass) for electron (e), proton (p), neutron (n) and alpha particle ($$\alpha$$) is:

2.68 $$\times$$ 10^-3 moles of a solution containing an ion Aⁿ⁺ require 1.61 $$\times$$ 10^-3 moles of $$MnO_4^-$$ for the oxidation of An⁺ to $$AO_3^-$$ in acid medium. What is the value of n?

When alpha particles are sent through a thin metal foil, most of them go straight through the foil because