Atomic Structure and Radiation EQE

Radioactive nuclei can emit alpha, beta or gamma radiation.

Which type of radiation is the most penetrating?

• Alpha (α)

• Beta (β)

• Gamma (γ)

Which type of radiation is the most ionising?

• Alpha (α)

• Beta (β)

• Gamma (γ)

Which type of radiation has the longest range in air?

• Alpha (α)

• Beta (β)

• Gamma (γ)

When radioactive isotopes in the Earth’s crust decay they release energy.

The decay causes the heating of rocks in the crust.

Figure 8 shows the decay of uranium–238 (U–238) into thorium–234 (Th–234).

Uranium 238 has 146 Neutrons and ​ (a)   protons

Thorium 234 has ​ ​ (b)   neutrons

• 92
• 144
• 238
• 234
• 90

Label the diagram

a

b

c

d

Proton

Atom

Nucleus

Electron

Neutron

Orbit

In every atom of the same element the positive charge is always the same. This is because the atoms all have the same number of ​ (a)   and these each have a ​ (b)   charge.

• protons
• positive
• neutron
• electron
• negative
• neutral

The results from the alpha particle scattering experiment led to the nuclear model.

Alpha particles were fired at a thin film of gold at a speed of 7% of the speed of light.

Determine the speed of the alpha particles.

Speed of light = 300 000 000 m/s

A hydrogen atom has a radius of 2.5 × 10^–11 m

Determine the radius of a magnesium atom.

From the diagram hydrogen atom has a radius of 10mm, the Magnesium atom has a radius of 55mm

What is the actual radius of the magnesium atom?

_.___ x 10^-10m

In an experiment, a beam of alpha particles was directed at a thin sheet of gold foil.

Most of the alpha particles passed straight through the gold foil.

Alpha particles which passed close to the nucleus of a gold atom did not pass

straight through.

What happened to the alpha particles which passed close to the nucleus of a

gold atom?

• Travelled straight through

• Bounced back

• Changed direction

• Changes speed

The results suggested that the diameter of the nucleus of a gold atom is 1/ 16000 of the diameter of the atom.

The diameter of a gold atom is 0.18 nm

Calculate the diameter of a gold nucleus in nm