Q: A sample of iodine-131 ($$^{131}\mathrm{I}) $$has a half-life of 8 days. If you start with 100 mg, how much remains after 24 days?

$$100 \times \left(\frac{1}{2}\$$right)^3$$ = 12.5 mg$$

Q: A patient receives a dose of technetium-99m with an activity of 40 mCi. If the effective half-life is 6 hours, how much activity remains after 18 hours?

$$40 \times \left(\frac{1}{2}\$$right)^3$$ = 5$$ mCi

Question 1

Which subatomic particle is responsible for the chemical identity of an element, and where is it located in the atom?

Accepted Answer

Proton; in the nucleus

Question 2

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many neutrons does it contain?

Accepted Answer

$$24 - 12 = 12$$ neutrons

Question 3

Which of the following statements best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 4

Given the symbolic notation $$^{37}_{17}\mathrm{Cl}$$, how many protons, neutrons, and electrons are present in this atom?

Accepted Answer

17 protons, 20 neutrons, 17 electrons

Question 5

Which type of radiation has the greatest penetrating power and requires thick lead or concrete for shielding?

Accepted Answer

Gamma ($$\gamma) $$rays

Question 6

A sample of iodine-131 ($$^{131}\mathrm{I}) $$has a half-life of 8 days. If you start with 100 mg, how much remains after 24 days?

Accepted Answer

$$100 	imes \left(\frac{1}{2}\$$right)^3$$ = 12.5 mg$$

Question 7

Which of the following nuclear equations correctly represents the alpha decay of americium-241?

Accepted Answer

$$^{241}_{95}\mathrm{Am} \$$rightarrow ^{4}$$_{2}\mathrm{He} $$+ ^{237}$$_{93}\mathrm{Np}$$

Question 8

Which unit is used to measure the biological effect of radiation on tissue?

Accepted Answer

Sievert (Sv)

Question 9

A patient receives a dose of technetium-99m with an activity of 40 mCi. If the effective half-life is 6 hours, how much activity remains after 18 hours?

Accepted Answer

$$40 	imes \left(\frac{1}{2}\$$right)^3$$ = 5$$ mCi

Question 10

Which statement best explains why iodine-131 is effective in treating thyroid cancer?

Accepted Answer

It emits beta particles that selectively destroy rapidly dividing thyroid cells.

Question 11

Which of the following is true about positron emission tomography (PET) scans?

Accepted Answer

They use fluorine-18, which emits positrons that interact with electrons to produce gamma rays.

Question 12

Which of the following best describes the difference between mass number and atomic mass?

Accepted Answer

Mass number is the sum of protons and neutrons in one atom; atomic mass is the weighted average of all isotopes.

Question 13

Which form of radiation is most dangerous if inhaled or ingested, but least dangerous outside the body?

Accepted Answer

Alpha ($$\alpha) $$particles

Question 14

A nuclear equation for the beta decay of manganese-56 is:

Accepted Answer

$$^{56}_{25}\mathrm{Mn} \$$rightarrow ^{0}$$_{-1}\mathrm{e} $$+ ^{56}$$_{26}\mathrm{Fe}$$

Question 15

Which of the following best explains why technetium-99m is widely used in medical imaging?

Accepted Answer

It emits gamma rays and has a short effective half-life, minimizing patient exposure.

Question 16

Which of the following is a correct statement about the biological effects of ionizing radiation?

Accepted Answer

Ionizing radiation can remove electrons from atoms, making them more reactive and potentially damaging cells.

Question 17

If a radioisotope has a half-life of 10 days, how much of a 160 mg sample remains after 30 days?

Accepted Answer

$$160 	imes \left(\frac{1}{2}\$$right)^3$$ = 20 mg$$

Question 18

Which of the following best describes a 'cold spot' in a lung scan using a radioisotope tracer?

Accepted Answer

An area where the tracer is not distributed, indicating nonfunctioning tissue.

Question 19

Which of the following is a correct symbolic notation for an atom with 15 protons, 16 neutrons, and 15 electrons?

Accepted Answer

$$^{31}_{15}\mathrm{P}$$

Atoms and Radioactivity: Structure, Isotopes, and Medical Applications

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