Radioactive Decay Chemistry

The half-life of cobalt-60 is 5.3 years. If a certain rock currently contains 10.0 g of cobalt-60, how much cobalt-60 will remain in the rock after 21.2 years?

0.63 g

The graph below shows the quantity of an unknown isotope versus time. What is the half-life of this isotope?

10 years

The half-life of a radioisotope is the amount of time that is required for half of the atoms in a given sample to undergo nuclear decay. What percent of the original radioisotope would remain after three half-lives have passed?

12.5%

What is produced when carbon-14 undergoes beta decay by releasing an electron?

14/7 N

The incomplete equation below shows positron emission from an isotope of fluorine. 18/9 F ---> ? + 0/+1 e Which daughter atom is missing from the equation?

18/8 O

The half-life of uranium-235 is 713 million years. Suppose a rock originally had 26 grams of uranium-235. A geologist had the rock tested, and found that it now has only 3.25 grams of uranium-235. Approximately how old is the rock?

2.1 billion years old

Potassium-40 has a half-life of 1.3 billion years. As the potassium-40 isotope decays, it becomes argon. If a rock was formed with 12 g of potassium-40, approximately how long would it take for 75% of the potassium-40 to be replaced by argon?

2.6 billion years

Cobalt-60 is a radioisotope that is sometimes used to sterilize medical equipment and medical wastes. If cobalt-60 has a half-life of 5.27 years, how long will it take before less than 5% of the original sample remains?

26.35 years

Each radioactive isotope has a specific half-life, or mode and rate of decay. Examine the graph below. What is the half-life of Strontium-90?

28.1 years

Strontium-90 is a dangerous substance that is released in nuclear weapon fallout. However, under controlled conditions, it can be used to treat bone cancer, and it can also be used as a radioactive tracer in medical and agricultural studies. If a scientist has 70 g of strontium-90, how many grams will remain after 4 half-lives?

4.375 grams

Which of the following correctly describes alpha and beta decay?

Alpha decay always involves emitting positive particles, and beta decay can involve emitting negative particles

Which of the following describes the process of gamma decay?

An excited atom releases a high-energy photon.

The equation below shows an isotope of magnesium going through a nuclear change. 23/12 Mg ---> 23/11 Na + 0/+1 e Which statement best describes this change?

Instability in the magnesium nucleus results in the emission of a positron.

Unstable isotopes undergo radioactive decay. What is something that can occur during radioactive decay?

Unstable isotopes can release charged particles.

Which of the following is a peaceful technological application of radioactive decay?

all of these

Which of the following types of nuclear decay produces particles that are identical to the helium nucleus?

alpha

What process is represented by the following equation? 232/90 Th ---> 228/88 Ra + 4/2 He

alpha decay

Which of the following types of radiation can pass through a sheet of paper?

beta and gamma

The letter X in the following equation represents an unknown particle. What process is represented by the equation? 118/54 Xe ---> X + 118/55 Cs

beta decay

Radiation can be emitted when the nuclear structure and/or the electron configuration of an atom is changed. Which of the following types of radioactive decay can release an electron from the nucleus?

beta emission

What type of radioactive decay can increase the atomic number of a radioactive atom?

beta emission

Which of the following is represented by the following symbol? 0/-1 e

electron

What type of particle is released during beta decay?

electron or positron

Which kind of radiation can penetrate clothing and skin to damage cells deep within a living body?

gamma

Which of the following types of radiation can pass through 10 cm of concrete?

gamma

Which of the following types of radiation can pass through a sheet of aluminum?

gamma

What type of radioactive decay involves only the release of high-energy photons and does not change the mass number or the atomic number of a radioactive isotope?

gamma emission

What type of radiation is the most dangerous because it can only be stopped by materials like thick concrete or lead?

gamma radiation

Which of the following is represented by the following symbol?

gamma radiation

Which of the following correctly organizes alpha particles, beta particles, and gamma radiation from the smallest relative mass to the largest relative mass?

gamma radiation → beta particles → alpha particles

For the following nuclear reaction, what was the beginning radionuclide (X)? X ---> 222/86 Rn + 4/2 He

radium-226

Radioactive isotopes are very unstable and undergo spontaneous nuclear reactions which emit particles and wavelike radiation. A large group of identical nuclei always decay at a predictable rate. This predictable rate of radioactive decay can be used

to estimate the age of materials that contain radioactive isotopes.

During alpha decay, a radioactive atom releases an alpha particle that is equivalent to the nucleus of a helium atom. So, the new atom that is formed should have an atomic number that is ______ than the original atom.

two less