8.3 - Nuclear Instability & Radius

Question 1

What are more stable, lighter or heavier elements?

Answer 1

Lighter.
Z < 20

Question 2

What are 4 things that will make a nucleus unstable?

Answer 2

• too many neutrons
• too many protons
• too many nucleons
• too much energy

Question 3

On an N against Z graph, what proves the sample is an alpha emitter?

Answer 3

• Occur beneath the line of stability when Z > 60 (too many nucleons)
• Number of protons > number of neutrons
• strong force between nucleons is unable to overcome the electrostatic force of repulsion between the protons

Question 4

On an N against Z graph, what proves the sample is a beta-minus emitter?

Answer 4

• Occur to the left of the stability line where isotopes are neutron-rich
• Neutron is converted to a proton

Question 5

On an N against Z graph, what proves the sample is a beta-plus emitter?

Answer 5

• Occur to the right of the stability line where the isotopes are proton-rich
• Proton is converted to a neutron

Question 6

On an N against Z graph, what proves the sample undergoes electron capture?

Answer 6

• When a nucleus captures one pf its own orbiting electrons
• occurs to the right of the stability line - proton-rich

Question 7

What is a nuclear excited state?

Answer 7

When an unstable nucleus decays, it may emit remaining energy in the form of a gamma photon. (does not change number of nucleons, just a release of energy)

Question 8

What is technetium-99m used for? (and what does the m stand for)

Answer 8

• Used as a gamma source in medical diagnoses
• The m stands for metastable - nucleus exists in a particularly stable excited state

Question 9

What are nuclear energy levels?

Answer 9

The nucleus, like the atom, has discrete energy levels whose location and properties are governed by the rules of quantum mechanics.