$$m = m_0$ \times \left(\frac{1}{2}\right)^n$$

Question 1

Which statement best defines an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 2

What determines the stability of an atom's nucleus?

Accepted Answer

The ratio of neutrons to protons.

Question 3

How many neutrons are present in a uranium nucleus with a mass number of 238 and atomic number 92?

Accepted Answer

146

Question 4

Which nuclear symbol correctly represents a chlorine nucleus with 17 protons and 20 neutrons?

Accepted Answer

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

Question 5

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have identical chemical properties but different physical properties.

Question 6

A radioactive isotope has a half-life of 8 days. If you start with 100 g, how much remains after 24 days?

Accepted Answer

12.5 g

Question 7

Which equation correctly describes the relationship between the remaining mass $$m of a $$radioactive sample and the number of half-lives $$n$$?

Accepted Answer

$$m = m_0$ 	imes \left(\frac{1}{2}ight)^n$$

Question 8

Which type of radiation requires the heaviest shielding for protection?

Accepted Answer

Gamma rays

Question 9

What change occurs in the nucleus when an alpha particle is emitted?

Accepted Answer

The atomic number decreases by 2 and the mass number decreases by 4.

Question 10

Which of the following best describes 'radioactive decay'?

Accepted Answer

The spontaneous transformation of an unstable atomic nucleus into a more stable one, often emitting radiation.

Question 11

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

Accepted Answer

0.25 g

Question 12

When a beta particle ($$\beta^-) is $$emitted from a nucleus, what change occurs?

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 radioactive isotopes in medicine?

Accepted Answer

Using radioactive tracers to diagnose and treat diseases.

Question 14

Which symbol correctly represents a beta particle?

Accepted Answer

$$\mathrm{^{0}_{-1}e}$$

Question 15

If a radioactive isotope decays from 24.0 grams to 0.75 grams, how many half-lives have occurred?

Accepted Answer

5

Question 16

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

Accepted Answer

Increased risk of genetic mutations and cancer.

Question 17

What happens to the atomic number and mass number when a positron ($$\beta^+) is $$emitted?

Accepted Answer

Atomic number decreases by 1; mass number remains unchanged.

Question 18

Which of the following best explains why gamma rays require more shielding than alpha or beta particles?

Accepted Answer

Gamma rays have no mass and no charge, allowing them to penetrate materials more deeply.

Question 19

Which type of nuclear decay does NOT change the atomic number or mass number of the nucleus?

Accepted Answer

Gamma decay

Question 20

Why might an atom undergo more than one type of radioactive decay before becoming stable?

Accepted Answer

Because a single decay may not bring the neutron-to-proton ratio into the stable range.

Isotopes, Radioactivity, and Nuclear Chemistry Study Guide

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