week 2

Question 1

Describe the structure of the atom and the nucleus

Answer 1

nucleus:
- protons (positive charge)
- neutrons (no charge)
- electrons (negative charge) orbits the nucleus

Question 2

explain the Bohr model of the atom

Answer 2

• electron energy is fixed by shell number and charge in the nucleus
• electrons can make transitions between shells and emit/absorb the energy difference
• this can be in the form of light, UV light, and x-rays (depending on difference between energy levels)

Question 3

what is electron binding energy and what two factors determine its strength

Answer 3

energy required to completely remove the electron from the atom (ionisation)
- more protons in nucleus -> stronger attraction (more pos)
- closer to nucleus -> stronger attraction

Question 4

what is the difference between ionisation and excitation of atoms

Answer 4

excitation (sometimes fluorescence) is the transition of electron to another shell, when there isn’t enough energy for complete removal

Question 5

what are the forces acting in the nucleus

Answer 5

electrostatic repulsive force
- two protons repel each other)
strong nuclear force
- attraction between neighbouring protons/neutrons
- stablises nuclei (balances repulsive force)

Question 6

why are some nuclei stable and others unstable

Answer 6

as the strong nuclear force balances the repulsive force, more neutrons are required as protons increase. at some point (protons>83) balancing is no longer possible and a nuclei becomes unstable (spontaneously break apart/rearrange internal structure). This is radioactivity