Radioactivity

Question 1

What is Radioactivity?

Answer 1

• The characteristic of various materials to emit ionising radiation. The phenomenon of spontaneous disintegration of unstable atomic nuclei to atomic nuclei to form more energetically stable atomic nuclei.

Question 2

What is ionisation?

Answer 2

The removal of electrons from an atom. The essential characteristic of high energy radiations when interacting with matter.

Question 3

What are Isotopes?

Answer 3

Atoms of the same species (same number of protons) which vary in neutron number.

Just because you have an isotope doesn’t mean it is radioactive.

The type of decay that a nuclide will typically undergo can be determined by its relationship to the line of stability.

Question 4

What are Isomers?

Answer 4

Two or more atomic nuclei that have the same atomic number and the same mass number but different energy states.

• The half-life of the isomers will be different.

Half-life is the amount of time taken for radioactivity to reduce to half.

• Cobalt-58 Isomer 1: 71-day half-life (decays by electron capture and positron emission) MORE DANGEROUS
• Cobalt-58m Isomer 2: 9-hour half life (decays by isomeric transition)

Question 5

What is Isomeric transition?

Answer 5

The decay of a nuclear isomer to a lower-energy nuclear state.

Question 6

What is meant by Metastable?

Answer 6

Gamma emission with a measurable half life.

Question 7

What is the Becquerel symbol?

Answer 7

The Becquerel symbol (Bq) is equal to one disintegration or nuclear transformation per second. 1 Bq = 1 s-1.

Question 8

What is the Curie unit?

Answer 8

A unit of radioactivity, equal to the amount of a radioactive isotope that decays at the rate of 3.7 × 1010 disintegrations per second.

Question 9

Describe Radioactive decay

Answer 9

Always follows an exponential decrease in activity with time.

Question 10

What is half life?

Answer 10

• The half-life (T1⁄2) describes the amount of time needed for half of a sample of unstable atoms or particles to undergo decay.
• You can not predict when a particular atom or particle will decay. You only know that, on average, half of a sample will decay during the span of one half-life.

Question 11

Describe radioactive decay

Answer 11

• All of the decays remove energy from the nucleus.
• Some release just energy.
• Some give energy to a particle which is emitted.

Question 12

List the types of Radioactive decay

Answer 12

• Alpha
• Beta
• Gamma

Question 13

Describe Alpha decay

Answer 13

-Alpha decay is the emission of an alpha particle (2 protons and 2 neutrons) from an unstable nucleus.
- 42He2+
- The daughter nuclide has an atomic number 2 less than the parent nuclide and a mass number 4 less than the parent nuclide.

Question 14

Describe beta decay

Answer 14

• Beta decay is the emission of a beta particle.
• There are two types of beta decay
• Beta minus
• Beta plus

Question 15

What is a beta minus?

Answer 15

• A b- particle is an electron.

• A neutron is converted to a proton and an electron.

• The electron b- particle is ejected.

n → p + b- + v_

V_ particle with no mass/charge only speed

Question 16

What is beta plus?

Answer 16

• A b+ particle is an positron.
• A proton is converted to a neutron and a positron.

• The positron b+ particle is ejected.

p → n + b+ + v

Question 17

What occurs during an electron capture?

Answer 17

• During electron capture, an electron in an atom’s inner shell is drawn into the nucleus where it combines with a proton to form a neutron and a neutrino.
• The neutrino is ejected from the atom’s nucleus.

p + e → n + v

Question 18

What is gamma emission?

Answer 18

• Gamma decay usually happens after the transmutation of the nucleus; the end product has to re-arrange the occupancy of energy levels in order to arrive at a more stable state.
• In the gamma decay, the emitted photon and recoil nucleus each have a well-defined energy after the decay.

Question 19

What is internal conversion?

Answer 19

• Internal conversion occurs when a gamma ray, emitted by the nucleus as it goes from the excited state to the ground state, interacts with one of the innermost electrons of the same atom.
• The electron is ejected from the atom