Atomic physics Year 11

The scattering of α-particles by a thin metal foil supports the nuclear model of an atom.

Why are α-particles used rather than neutrons?

• because they always travel more slowly

• because they are heavier

• because they are larger in diameter

• because they have a positive charge

A nucleus of a radioactive substance  $_{84}^{218}Po\$  undergoes an α-decay followed by a β-decay.
What are the nucleon (mass) number (A) and proton (atomic) number (Z) of the nuclide formed after both decays have happened? 

• A=214, Z=85

• A=216, Z=85

• A=214, Z=83

• A=216, Z=83

Fig. 12.1 shows a decay curve for polonium-210.

Use the graph to determine the half-life of polonium-210.

half-life = _____ weeks

The half-life of carbon-14 is 5800 years.

A piece of wood contained 20 000 carbon-14 atoms when it was buried in a landslide.

Calculate the number of years it takes until the number of carbon-14 atoms in the wood is 2500.

(a) Fig. 12.1 represents an atom of carbon.
(i) State the name of particle X.
(ii) State the name of particle Y.
(b) Carbon-14 is unstable. It decays by beta emission to form nitrogen.
Complete the equation for this decay. $_6^{14}C\ \ \rightarrow\ _Z^AN\ \ +_{-1}^0e\$ 

A= ...

Z= ...

Describe how an electric field between two charged plates could be used to determine whether a beam of particles consists of α- or β-particles.

Below are four statements about isotopes of a certain element.

Which statement about the isotopes must be correct?

• They are radioactive.

• They are unstable.

• They have the same number of neutrons.

• They have the same number of protons.

Sodium-24 decays to magnesium-24 according to the following equation. $_{11}^{24}\ Na\ \ →\ \ _{12}^{24}\ Mg\ +\ emitted\ particle$  
What is the emitted particle?

• α-particle

• β-particle

• neutron

• proton

Which diagram represents an experiment that provided evidence for the nuclear atom?

• 
• 
• 
• 

The counter of a radiation detector placed close to a radioactive source gives a count rate of 1600 counts / s. The half-life of the source is 1 week.

Ignoring background radiation, calculate the count rate

(i) 1 week after the first measurement,

(ii) 3 weeks after the first measurement.