1.7: Radioisotopes

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Which of the following subatomic particle ratios is important to maintain nuclear stability?
1. neutron/proton
2. proton/electron
3. negatron/neutron
4. positron/electron
5. neutron/alpha
Characteristic X-rays are emitted during the nuclear reaction involving:
1. gamma decay
2. positron decay
3. electron capture
4. negatron decay
5. none of the above
If decay factors for a radionuclide 8 days and 16 days after the calibration date are 0.9 and 0.8 respectively, what will be the radioactivity of 1 millicurie of this radionuclide 24 days from now?
1. 0.72 microcurie
2. 0.072 millicurie
3. 0.170 millicurie
4. 0.89 millicurie
5. 0.72 millicurie
A crystal scintillation detector is primarily used for detecting radionuclides emitting:
1. positrons
2. gamma rays
3. negatrons
4. X-rays
5. ultraviolet light
Beta emission is the emission of:
1. a proton
2. an electron
3. a neutron
4. a ray of light of very short wavelength
5. an X-ray
Specific activity is the radioactivity as expressed in disintegrations/second per mole of a compound or atom. Which of the following has the highest specific activity?
1. ¹²⁵I (t_1/2 = 60 days)
2. ³⁵S (t_1/2 = 62 days)
3. ³H (t_1/2 = 12 years)
4. ¹⁴C (t_1/2 = 5000 years)
5. ¹³¹I (t_1/2 = 8 days)
Gamma emission is the emission of:
a. a proton
b. an electron
c. a neutron
d. a ray of light of very short wavelength
e. an X-ray
In the radioactive decay of ³H atom to a ³He atom, the subatomic particle emitted from the nucleus is a (an):
1. alpha particle
2. electron (negatron)
3. positron
4. gamma ray
5. neutron
A secondary scintiliator (e.g., POPOP) is used in liquid scintillation counting:
a. to facilitate dissolution of the sample
b. to obtain a homogenous scintillation mixture
c. to enhance the counting efficiency by “wavelength shifting”
d. as the internal standard
e. to reduce chemiluminescence
¹²⁵I is used as a label because:
a. it has high specific activity
b. it is a high-energy emitter
c. it has a long half-life
d. all of the above
e. none of the above

Use the following Key to answer Questions 11 through 17

1,2, and 3 are correct
1 and 3 are correct
2 and 4 are correct
only 4 is correct
all are correct

¹²⁵I-labeled ligands are preferable to ³H-labeled ligands in radioimmunoassays because of:
1. longer shelf life
2. higher specific activity
3. lower cost
4. gamma-emission
During the course of radioactive decay, a proton is converted to a neutron in:
1. beta decay
2. alpha decay
3. electron capture
4. positron decay
Scintillation counters measure light pulses. These light pulses are related to:
1. ionizing radiation
2. high-energy gamma rays
3. high-energy beta particles
4. random electrons
The most commonly encountered radioactive emissions in the hospital laboratory are:
1. alpha -1 and gamma
2. alpha -1 and beta
3. beta + and gamma
4. beta - and gamma
The most commonly used radioisotope(s) in the chemistry laboratory is/are:
1. ¹²⁵I
2. ³⁵S
3. ³H
4. ¹⁴C
Radioisotopes are most commonly used to measure in antibody-based competitive assays:
1. metals
2. antibodies
3. electrolytes
4. antigens
Instrumentation used for detecting and recording beta-emitting isotopes differs from that used for gamma emitters because a beta scintillation counter requires:
1. a photomultiplier tube
2. a hollow cathode lamp
3. a sodium iodide crystal
4. presence of a fluor

Answer

a (p. 190)
c (p. 190-191)
e (p. 191-192)
b (p. 194)
b (p. 190)
e (p. 192)
d (p. 191)
b (p. 190)
c (p. 196)
a (p. 192)
c (p. 192)
d (p. 190)
c (p. 194)
d (p. 192)
e (p. 192)
c (p. 189)
d (p. 194-197)

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