Radioactive Modes of Decay

Question 1

Radioactive Decay

Answer 1

Spontaneous nuclear transformation in an unstable nucleus that results in the formation of a new atom

Unstable atom releases matter and/or energy during a transition to a more stable form.

Unstable atoms are also known as radioactive atoms, radionuclides

Question 2

Curie

Answer 2

The activity of that quantity of radioactive material in which 3.7x10^10 atoms are transformed in one second

Based on 1 gram of Ra-226

Question 3

Becquerel (Bq)

Answer 3

Unit of radioactivity in the international system (SI) of units

One disintegration per second (dps).

1 Ci= 3.7 x 10^10 Bq

SI units are normally expressed in large multiples like mega-Becquerel (MBq) or giga-Becquerel (GBq)

Question 4

Physical Half-life (t1/2)

Answer 4

Time required for the activity of a given radioactive nuclide to decrease to one-half it initial value due to radioactive decay

Question 5

Half Life of Co-60

Answer 5

5.27 y

Question 6

Biological Half-Life (T1/2bio)

Answer 6

Time required for the body to eliminate, by natural means, one half of the material

Question 7

Effective Half-Life (T1/2eff)

Answer 7

Time required for a radioactive element in the body to be diminished by 50%. Combination action of radioactive decay and biological elimination

Question 8

Radioactive decay formula

Answer 8

Af= Ao^e-lnT

Af- final activity
Ao- original activity
LN- decay constant (ln(2)/t1/2 or 0.693

Question 9

Alpha Decay

Answer 9

Alpha particle is emitted from the nucleus. Daughter may be left in an excited state and de-excite emitting a gamma

Instability- too many nucleons in the nucleus

Follows- Z - X - A

Question 10

Beta - decay

Answer 10

Neutron is converted into proton, electron, and antineutrino. Daughter may be left in excited state and de-excite emitting a gamma.

Condition of instability- neutron to proton ratio to high

Antineutrino- no charge and is nearly massless and very weakly interacts with matter.

Beta- = Z-X-A

Question 11

Beta + Decay

Answer 11

Proton is converted into a neutron, positron, neutrino. The positron and neutrino are emitted from nucleus. Daughter may be left in excited state and de-excite emitting a gamma.

Instability- neutron to proton ratio to low

Has annihilatation reaction, due to combining with electron. The destruction causes to gamma ray of 0.511 MeV each in opposite directions

Question 12

Gamma decay

Answer 12

Occur if the daughter nucleus is left in excited state. Emits gamma, may be immediate or delayed.

Question 13

Metastable decay

Answer 13

Is a gamma decay that occurs a microsecond or more after initial decay