10.1 radioactivity. nuclear decay… atoms of one element can change into atoms of a different...

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Page 1: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

10.1 Radioactivit

y

Page 2: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

Nuclear Decay…• Atoms of one element can change into atoms of a

different element altogether. • An unstable atom has excess internal energy, with the

result that the nucleus can undergo a spontaneous change towards a more stable form.

• Radioisotopes are atoms that contain an unstable nucleus and will change into another isotope over time.

• Scientists can estimate the age of fossils by looking at nuclear decay.

Page 3: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

Radioactivity… is the process in which

an unstable atomic nucleus emits charged particles and energy.

Page 4: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

3 Types of Nuclear Radiation

1. Alpha Particles2. Beta Particles3. Gamma Rays

Page 5: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

Nuclear Radiation…charged particles and energy

that are emitted from the nuclei of radioisotopes.

• If an element decays and emits an alpha or beta particle, it becomes a new element.

• Gamma rays are often emitted with alpha or beta radiation also, as the nucleus decays to a less excited state.

Page 6: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

Alpha Particle• Positively charged particle made up of two protons and two neutrons—the same as a helium nucleus. • When a uranium-238 sample decays, it emits alpha particles. • An alpha particle has a

2+ charge. • Symbol for alpha:

Page 7: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

Beta Particle• negatively charged radiation• electron emitted by an

unstable nucleus• A beta particle is assigned an atomic number of –1.• Symbol for beta:

Page 8: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

Gamma Ray• Penetrating ray of energy emitted by an unstable nucleus. • Gamma radiation has no mass and no charge. • Like X-rays and visible light, gamma rays are energy waves that travel through space at the speed of light.•Symbol for gamma:

Page 9: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

Page 10: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

Units of Radioactivity…• The amount of radioactive material is given in

becquerel (Bq), a measure which enables us to compare the typical radioactivity of some natural and other materials.

• A becquerel is one atomic decay per second.

Page 11: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

Radioactivity of some natural and other materials

• 1 adult human (100 Bq/kg) 7000 Bq • 1 kg of coffee 1000 Bq • 1 kg superphosphate fertiliser 5000 Bq • The air in a 100 sq metre Australian home (radon) 3000 Bq • The air in many 100 sq metre European homes (radon) up to 30 000 Bq • 1 household smoke detector (with americium) 30 000 Bq • Radioisotope for medical diagnosis 70 million Bq • Radioisotope source for medical therapy 100 000 000 million Bq (100 TBq) • 1 kg 50-year old vitrified high-level nuclear waste 10 000 000 million Bq (10

TBq) • 1 luminous Exit sign (1970s) 1 000 000 million Bq (1 TBq) • 1 kg uranium 25 million Bq • 1 kg uranium ore (Canadian, 15%) 25 million Bq • 1 kg uranium ore (Australian, 0.3% 500 000 Bq • 1 kg low level radioactive waste 1 million Bq • 1 kg of coal ash 2000 Bq 1 kg of granite 1000 Bq

Page 12: 10.1 Radioactivity. Nuclear Decay… Atoms of one element can change into atoms of a different element altogether. An unstable atom has excess internal

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