EXAM QUESTIONS FOR RADIOISOTOPES
1. (6 pts) What is the difference between atomic number and mass number? Which
of these two numbers determines the IDENTITY OF AN ELEMENT?
Atomic number is the # of protons in an atom(2 pts)
This determines identity. (2 pts)
Mass number is the # of protons + # neutrons in an atom. (2 pts)
2. (4 pts) How can the process of nuclear disintegration result in the change of the
IDENTITY of an element? Be specific.
Usually either a Neutron disintegrates to a proton + an electron OR
a neutron gives up an electron to become a proton.(2 pts for how it works)
Either way, the atomic number, and therefore the elemental identity, changes. (2 pts for
how identity changes)
3. (4 pts) What is an isotope?
Different nuclear configurations of an element
4. (4 pts) What is a radioisotope?
An isotope that is capable of undergoing nuclear decay
5. (16 pts) Circle the correct response:
a.) TRUE / FALSE: All types of radiation are external hazards.
b.) TRUE / FALSE: All types of radiation are internal hazards.
c.) TRUE / FALSE: -particles are more penetrating because they are larger
particles than alpha particles
d.) TRUE / FALSE: -particles are less hazardous because they do not
penetrate
the layer of dead skin of the body
e.) TRUE / FALSE: gamma rays are the most penetrating form of radiation
f.) TRUE / FALSE: When working with beta-emitters, you must always use
Lucite shielding
g.) TRUE / FALSE: -particles are the most serious internal hazard to the body
h.) TRUE / FALSE: When a radioisotope releases an -particle, that isotope
turns into a different element.
6. (6 pts) You are going to be doing an experiment involving radioactivity. Your coworker is telling you about your likely level of exposure. Is it more useful for him to
provide you that information in rad or rem? EXPLAIN WHY THE UNIT YOU
HAVE CHOSEN IS MORE USEFUL.
Rem is more useful (3 pts)
Rem is rad corrected by a quality factor, Q, that corrects for the different damaging
effects of different types of radiation. (3 pts)
7. (4 pts) What is a “physical half-life”?
The time it takes for a radioisotope to decay to one-half its original amount
8. (4 pts) Suppose you start with 1000 atoms of a radioisotope with a half-life of 7 days
on February 1st. How many atoms of radioisotope will remain on March 1st? SHOW
YOUR WORK.
28 days = 4 half lives (2 pts)
1000 to 500
500 to 250
250 to 125
125 to 62.5 molecules (2 pts)
9. (4 pts) What is meant by the ACTIVITY of a radioactive sample?
The number of decays per unit time
10. (8 pts) What is the difference between a “stochastic” versus a “non-stochastic” effect
of radiation exposure? Provide ONE example of each type of effect.
A stochastic effect arises from injury to one or a few cells. It is an “all or none” effect.
Increased radiation dose increases the PROBABILITY of the effect occurring, not the
SEVERITY of the effect. (2 pts)
(CANCER) is a stochastic effect (2 pts)
A non-stochastic effect increases in severity with increasing dose. (2 pts)
(RADIATION BURNS) is a non-stochastic effect (2 pts)
11. (4 pts) What is a BIOLOGICAL HALF-LIFE?
The time required for the body to reduce the amount of a chemical or substance to onehalf its original amount.
12. (6 pts) Suppose you accidentally ingest a radioisotope. Provide TWO factors that
will affect how much damage this ingestion does to your body.
Type of radiation, physical half-life, biological half-life, elemental form or incorporated
into a compound, metabolized or incorporated into an organ (2 pts each)
13. (5 pts) Provide TWO assumptions about the current no-threshold model of risk
assessment that make it likely that the calculated risks associated with working with low
levels of radioactivity are an OVERESTIMATE of the true risks.
Assumes no cellular repair(3 pts) and extrapolates from acute exposures in a linear
fashion to estimate effects of low level radiation exposure (no threshold) (2 pts).
14. (10 pts) Suppose you receive a dose of 16 rad from a source that is positioned 1 foot
from you. How many rad will you receive if you move to a distance that is 4 feet from
the source?
16 rad X 1/16 = 1 rad
15. (5 pts) Suppose you are going to work with an alpha emitter. What type of shielding
is required?
No shielding. Can not penetrate skin.
16. (5 pts) Suppose you are going to work with a high energy beta emiiter. What type of
shielding is required?
Plastic, Lucite shield of varying thickness
17. (5 pts) Considering the REASON that radiation is damaging, what is the purpose of
using shielding? (Why does it protect the worker?)
. Shielding allows another material other than body tissue to absorb the dose