physics : atomic structure paper 1

How do electrons jump to a higher level/shell?

If they gain enough energy through electromagnetic radiation.

How to electrons fall down a level/shell?

After moving up a shell, they eventually fall back and re emit energy as electromagnetic radiation.

How are electrons arranged?

In a series of energy levels (shells). Each shell is further away from the nucleus, increasing energy level.

What is the half life?

Time taken for the number of decays (activity) to half.

What is the activity?

Overall rate of decay for all the isotopes in our sample

What is activity measured in?

Bq = Becquerels

1 becquerel = 1 decay per second.

What happens to the number of unstable particles as time goes on?

The number of unstable particles remaining decreases. And the overall rate of decay (activity) also decreases.

What are the advantages and disadvantages of nuclear energy?

Advantages: uranium/plutonium fuel is cheap; produces large steady amounts of energy; it’s a clean energy = no greenhouse gas produced.

Disadvantages: nuclear plants expensive to build; nuclear waste expensive to get rid of (must be buried in special bunkers); risk of disaster → people weary.

Describe the fission chain process:

Nuclear fission leads to chain reaction.

1st fission triggers more fission which then triggers even more fissions and so on.

What energy is needed for nuclear fission? How much is needed?

Lots of gamma radiation energy needed.

What happens if nuclear fission isn’t controlled?

Whole system can fail, leading to large amounts of energy to be released (a nuclear bomb).

What is radiation sickness?

If cells receive too much radiation, they can be killed off completely. This can lead to radiation sickness → vomiting, fatigue, hair loss.

What might doctors use radiation for?

Destroying particular cells, like cancer cells.

What is external and internal radiotherapy?

Externally : gamma ray - only cancer get’s highest dose.

Internally : beta ray - radio source inside body (inside/next to cancer)

What are the side effects of radiotherapy?

Healthy cells can get killed/damaged, leading to radiation sickness.

What is nuclear fission?

The splitting of a large unstable nuclei into smaller nuclei. This releases lots of energy.

What is nuclear fission that is spontaneous?

Happens by itself, which is very rare.

What happens when absorbing a neutron in nuclear fission?

Nucleus is split by making it less stable.

How does nuclear fission in reactors work?

Neutrons used to get process started.

What is the difference between nuclear fusion and nuclear fission?

Nuclear fusion: fusing of light nuclei to make heavy nuclei; releases tons of energy; only happens in stars → high temperature/pressure needed.

Nuclear fission: large unstable nuclei split into smaller nuclei; produces lots of energy (less than fusion); used on earth to generate electricity.

What is nuclear fusion?

Two lighter nuclei fuse together to form single large nucleus. This releases lots of energy and is a process that fuels stars.

What process explains why all elements are heavier than hydrogen?

Nuclear fusion.

Why does nuclear fusion produce large amounts of energy?

Due to some of the nuclei mass being converted to energy.

What is irradiation?

The princes by which an object is exposed to any radiation (ionising/non-ionising). It isn’t harmful.

Why do people worry about irradiated things (e.g. food)?

They think it will make you mutated or make you radioactive. They think it will spread.

Who discovered the Nuclear Model? When?

Ernest Rutherford - 1909

What is the nuclear model?

A compact nucleus (positive charge) with a negative charge cloud around it.

Describe how the nuclear model was made?

Positively charged alpha particles fired at a thin sheet of gold.

What is contamination?

When radioactive particles get onto objects. Contamination isn’t a problem, but that the radioactive material is likely to decay. Meaning it’s more harmful.