Nuclear Chemistry
The graph below shows the quantity of an unknown isotope versus time. What is the half-life of this isotope?
10 years
Uranium-238 is a radioactive form of uranium that has a half-life of 4.51 x 109 years. If a scientist has an initial sample of 200 g of uranium-238, how much will remain after one half-life?
100 g
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
Which of the following equations is an example of nuclear fusion?
2H + 3H 4He + neutron
Which of the following reactions is a fusion reaction?
2H1 + 3H1 4He2 + 1n0
Which of the following correctly describes the charge of beta particles and alpha particles?
Alpha particles are positively charged, and beta particles are negatively charged.
Which of the following describes the process of gamma decay?
An excited atom releases a high-energy photon.
All elements have isotopes. That is, although all atoms of an element have the same number of protons, some of the atoms have a different number of neutrons.If the nucleus of the isotope is unstable, the isotope is radioactive. Radioactive isotopes have a tendency to undergo spontaneous radioactive decay until they form an atom with a stable nucleus.Which of the following statements is true regarding spontaneous radioactive decay? I.Spontaneous radioactive decay occurs more frequently in atoms with large nuclei, although it can occur in atoms with small nuclei. II.Radioactive decay processes can result in the formation of an alpha particle (helium nucleus) or a beta particle (electron). III.When radioactive isotopes decay, they form atoms of different elements. IV.Radioactive elements can undergo more than one decay, or transmutation, in order to form a stable nucleus.
I, II, III, and IV
Which of the following occurs during radioactive decay?
The mass of the radioisotope decreases.
Which of the following best describes nuclear fusion?
Two or more atoms are forced together to form a heavier atom.
Unstable isotopes undergo radioactive decay. What occurs during radioactive decay?
Unstable isotopes release charged particles.
Which of the following is a product of nuclear fusion reactions?
a nucleus with greater mass
A radioactive atom has just undergone nuclear decay. Its mass number is now four less than the original atom. Which type of nuclear decay has occurred?
alpha
Which of the following types of nuclear decay produces particles that are identical to the helium nucleus?
alpha
Three samples are emitting different types of radiation. Some properties of each radiation type are shown in the table below. Which type of radiation is Sample 3 emitting?
alpha particles
High-energy electromagnetic waves are released when an atom undergoes gamma decay. Which of the following is usually ejected simultaneously with gamma radiation?
an alpha or a beta particle
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
Three samples are emitting different types of radiation. Some properties of each radiation type are shown in the table below. Which type of radiation is Sample 1 emitting?
beta particles
What type of particle is released during beta decay?
electron
In stars, hydrogen nuclei combine with each other to form helium and other heavier elements. What is this process called?
fusion
In stars, hydrogen nuclei combine with each other to form helium and other heavier elements. What is this process called?
fusion
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
Three samples are emitting different types of radiation. Some properties of each radiation type are shown in the table below. Which type of radiation is Sample 2 emitting?
gamma rays
Which of the following elements is most likely to be used in a nuclear fusion reaction?
hydrogen
Which of the following particles can pass through concrete? I.alpha II.beta III.gamma
none of these
Which of the following uses nuclear fusion?
the reactions in the Sun
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
