22.2 Nuclear Decay

When an alpha particle is emitted by a radioactive nucleus, which of the following changes occurs to the nucleus?

• The number of protons decreases by four.

• The number of protons decreases by two.

• The number of neutrons decreases by four.

• The number of nucleons increases by two.

When a negatively-charged beta particle is emitted by a radioactive nucleus, which of the following changes occurs to the nucleus?

• The number of protons increases by one.

• The number of neutrons increases by one.

• The number of nucleons increases by one.

• The number of nucleons decreases by one.

Which radiation is the least penetrating?

• alpha

• beta

• gamma

• neutron

During beta decay, what particles are needed for momentum and energy to be conserved?

• electrons

• positrons

• neutrinos or antineutrinos

• neutrons

What does X represent in the nuclear decay formula: ²³²₉₀Th ---> X + ⁴₂He??

• ²³²₉₀Ra

• ²²⁸₈₈Ra

• ²²⁸₈₈Th

• ²²⁸₈₈He

What does X represent in the nuclear decay formula: ¹⁴₆C ---> X + ⁰_-1e?

• ¹⁴₇N

• ¹⁴₇C

• ¹⁴₈O

• ¹⁴₆N

How many half-lives does it take for a radioactive substance to decay to 25 percent of its original amount?

• 1

• 2

• 3

• 4

A radioactive sample containing 24 g of material undergoes a decay process. After three half-lives have passed, how much of the original substance remains?

• 24 g

• 12 g

• 6 g

• 3 g

Give the rules of nuclear decay, what properties must be conserved in a nuclear decay process.

• the total of the atomic numbers and the mass numbers on the left side of the equation must be the same as the total of the atomic numbers and the mass numbers on the right side

• the total of the atomic numbers on the left side of the equation must be the same as the total of the mass numbers on the right side

• the total of the atomic numbers on the left side of the equation must be less than the total of the atomic numbers on the right side

• the total of the atomic numbers on the left side of the equation must be greater than the total of the atomic numbers on the right side

The half-life of astatine-218 is 1.6 s. If a sample of astatine-218 contains 1.6 x 10¹⁷ nuclei, how many nuclei, in becquerels, will decay each second?

T_1/2 = 0.693/λ

Activity = λN

• 1.1 x10¹⁷ decay/s or 1.1 x10¹⁷ Bq

• 6.9 x 10¹⁶ decay/s or 6.9 x 10¹⁶ Bq

• 3.7 x 10¹⁶ decay/s or 3.7 x 10¹⁶ Bq

• 0.69 x 10¹⁷ decay/s or 0.69 x 10¹⁷ Bq