Atomic Physics

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=214, Z=85

• A=216, Z=85

• A=214, Z=83

• A=216, Z=83

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NGSS.HS-PS1-8

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

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

half-life = _____ weeks

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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.

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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.

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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.

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• α-particle

• β-particle

• neutron

• proton

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NGSS.HS-PS1-8

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

• 
• 
• 
• 

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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.

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