1.1. A fluorescent tube is filled with mercury vapour at low pressure. One particular mercury atom has its electron ground state fully occupied.

Explain what is meant by the term ‘ground state’.

1.2. Figure 1 shows energy levels of a mercury atom:

Figure 1   

One of the ground state electrons absorbs a photon and moves up an energy level, from n = 1 to n = 2.  

After a short amount of time, it moves back down an energy level, from n = 2 to n = 1, and emits a photon. 

Determine the energy of the photon released.

1.3. Draw an arrow on Figure 1 to show a transition which emits a photon of a greater frequency than the photon emitted in part (b).

1.4. Figure 2 shows the emission spectra of mercury:

Emission spectra are formed by collecting photons emitted from de–exciting electrons in atoms. 

With reference to energy levels, describe the evidence an emission spectra like that in Figure 2 provides for the structure of atoms.