$$2.00 \times \left(\frac{1}{2}\$$right)^3$$ = 0.25$$ grams

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

Question 1

Which of the following best defines an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 2

What primarily determines the stability of an atomic nucleus?

Accepted Answer

The ratio of neutrons to protons in the nucleus.

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes are atoms of the same element with different numbers of neutrons.

Question 4

A nucleus of uranium has a mass number of 238. If its atomic number is 92, how many neutrons does it contain?

Accepted Answer

$$238 - 92 = 146$$

Question 5

Which of the following is the correct nuclear symbol for a chlorine atom with 17 protons and 20 neutrons?

Accepted Answer

$$\$$displaystyle ^{37}$$_{17}\mathrm{Cl}$$

Question 6

Which of the following best describes radioactive decay?

Accepted Answer

The spontaneous breakdown of an unstable atomic nucleus, releasing particles or energy.

Question 7

What is the definition of half-life?

Accepted Answer

The time required for half of the atoms in a radioactive sample to decay.

Question 8

A 2.00 gram sample of radium-226 has a half-life of 1600 years. How much of the sample will remain after three half-lives?

Accepted Answer

$$2.00 	imes \left(\frac{1}{2}\$$right)^3$$ = 0.25$$ grams

Question 9

A 100 g sample of a radioactive isotope has a half-life of 8 days. How much remains after 24 days?

Accepted Answer

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

Question 10

Which type of radiation requires the heaviest shielding to protect against exposure?

Accepted Answer

Gamma radiation

Question 11

What happens to the atomic number and mass number of a nucleus when it emits an alpha particle?

Accepted Answer

Atomic number decreases by 2, mass number decreases by 4.

Question 12

Which of the following best describes what happens when a beta particle is released from an unstable nucleus?

Accepted Answer

A neutron is converted into a proton, increasing the atomic number by 1.

Question 13

Which of the following is a real-world application of carbon-14 isotopes?

Accepted Answer

Determining the age of ancient artifacts through radiocarbon dating.

Question 14

Which of the following is a risk associated with exposure to gamma radiation?

Accepted Answer

It can penetrate deeply into tissues and damage internal organs.

Question 15

Which of the following nuclear reactions represents beta decay?

Accepted Answer

$$\$$displaystyle ^{14}$$_{6}\mathrm{C} \$$rightarrow ^{14}$$_{7}\mathrm{N} $$+ ^{0}$$_{-1}\mathrm{e}$$

Question 16

Which of the following statements about alpha particles is correct?

Accepted Answer

They consist of 2 protons and 2 neutrons and are stopped by paper.

Question 17

When a positron is released from an unstable nucleus, what change occurs in the nucleus?

Accepted Answer

A proton is converted into a neutron, decreasing the atomic number by 1.

Question 18

Which of the following best explains why nuclear radiation can be damaging to living organisms?

Accepted Answer

It can ionize molecules in cells, leading to mutations and cell death.

Question 19

Which of the following is a correct description of the use of isotopes in medicine?

Accepted Answer

Radioactive isotopes are used in imaging and treatment, such as using iodine-131 for thyroid disorders.

Question 20

Which of the following statements about beta particles is correct?

Accepted Answer

They are high-energy electrons emitted from the nucleus during radioactive decay.

Isotopes, Nuclear Chemistry, and Radioactivity Study Guide

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