Physics, 4.4- Atomic structure and radioactivity

Ancient greek believe atom is a tiny sphere which can not be divided.

Describe how plum-pudding model replace the idea of atom. [3 marks]

• Electron discovered.

• This show atom have internal structure.

• Plum-pudding model suggest that atom is is a ball of positive charge with negative electron embedded in it.

Explain how the result of alpha-scattering experiment create a nuclear model of atom.

[6 marks]

Most alpha particle pass through the gold foil- atom made of mostly empty space.

Some alpha particle deflected- nucleus is positively charged.

Some alpha particle bounced back- the mass is concentrated at the centre.

Fill the correct word from earliest discovery to latest discovery. [2 marks]

_____ → _____ → _____ → _____

Electron, Proton, Neutron, Electron orbit.

Electron → Proton → Electron orbit → Neutron

What is meant by ‘radioactive decay’.[2 marks]

Unstable nucleus gives out radiation.

State 4 type of nuclear radioactive. [4 marks]

Alpha particle, Beta particle, Gamma radiation, and Neutron.

What is meant by ‘nuclear fusion’. [2 marks]

Two light nuclei are joined to form heavier nucleus.

Describe the process of chain reaction of nuclear fission. [5 marks]

• Nucleus absorb neutron.

• Nuclear fission and form two nuclei.

• Emit two or three neutron and gamma rays.

• The neutron may have enough kinetic energy.

• To start to be absorbed by more nuclei and trigger nuclear fission.

Give two natural source of background radiation. [2 marks]

Radioactive rock and cosmic wave

What is meant by ‘irradiation’. [1 mark]

Exposing an object to nuclear radiation.

What is meant by ‘contamination’. [1 mark]

Unwanted radioactive isotopes end on other material.

What is meant by ‘half-life’. [1 mark]

The time it takes for the number of nuclei to halve.

State one safety precaution to reduce the radiation dose that recieve. [1 mark]

Wear lead apron.