51 Questions
What is a nuclear fusion reaction?
A reaction where two light nuclei combine to form a heavier nucleus
In a nuclear fission reaction, what happens?
A heavy nucleus splits into two lighter nuclei
Which of the following is an application of radioactivity in medicine?
Detecting and treating tumors
How is the number of mass conserved in nuclear reactions?
The sum of the masses of the reactants equals the sum of the masses of the products
What does the equation $^{235}U + ^1n \rightarrow ^{139}Xe + ^{95}Sr + 3 ^1n$ represent?
Fission reaction
Which of the following statements is true about the nuclear fusion reaction $^2H + ^3H \rightarrow ^4He + ^1n$?
Two light nuclei combine to form a heavier nucleus and a neutron
What is the unit of measurement for the activity of a sample?
Becquerel
Which device is used to measure the activity of a sample?
Geiger-Muller counter
What is the radioactivity level of uranium ore?
25,000,000 Bq/kg
How long is the half-life (t1/2) of Cesium-137?
30 years
What property does the half-life of a radioactive isotope affect?
Its decay rate over time
Which application of radioactivity is used to diagnose cancers?
Scintigraphy
What technique is used to determine the age of an ancient object by measuring its activity?
Carbon dating
Which radioactive element is used as a fuel in nuclear power plants?
Uranium
Who discovered radioactivity in 1896?
Henri Becquerel
What type of reactions result from nucleus instability?
Spontaneous nuclear reactions
What is emitted during the disintegration of a parent nucleus?
A nucleus or a ray
How is the activity of a radioactive sample measured?
Using a Geiger counter
What is an example of nuclear fission?
Fission of Uranium 235
What is the product of the fusion of $^2_1H$ and $^3_1H$?
$^4_2He$ and $^1_0n$
Which application is NOT among those listed for radioactivity?
Generating wind energy
Which particles cause ionizations when passing through living matter?
All of the above
What is the unit of measurement for the activity of a sample?
Becquerel (Bq)
Which process describes the exponential decrease of activity over time?
Radioactive decay
What is the half-life of a radioactive isotope?
Time taken for the activity to decrease to half its initial value
Which of the following is a medical application of radioactivity?
Treating tumors with radiotherapy
Which element is mentioned as a fuel in nuclear power plants?
Uranium
What term is used for applying radioactivity to determine the age of ancient objects?
Carbon dating
What type of particle is emitted during alpha decay?
Helium nucleus
What material can stop beta particles?
Aluminum sheet
What happens during a beta-minus ($\beta^-$) decay?
A neutron transforms into a proton
Which type of radiation is the most penetrating?
Gamma rays
What does the gamma radiation emitted by atoms consist of?
Electromagnetic waves
What are the laws of conservation during a nuclear reaction?
Conservation of mass number and charge
Where are stable nuclides located on the Segre diagram?
At the center of the stability band
What is the symbol for the alpha particle?
$^4_2He$
What is the result when a neutron strikes a ${}^{235}U$ nucleus?
${}^{235}U$ becomes unstable and splits into lighter nuclei, releasing energy and more neutrons.
Which smaller nuclei can be produced from the fission of ${}^{235}U$?
${}^{141}Ba$ and ${}^{92}Kr$
What is a chain reaction in the context of nuclear fission?
A continuous series of fission reactions caused by released neutrons striking other uranium nuclei.
What is one application of fission reactions?
Generating electricity in nuclear power plants.
Which element is commonly used as a fuel in fission reactions?
Uranium
What does the symbol A represent in a nucleus?
Number of nucleons (mass number)
What is the charge of a single proton?
1.602 * 10^-19 C
How can isotopes be characterized?
Same number of protons but different number of nucleons
What ensures the cohesion of the nucleus against electrical repulsive forces?
Strong interactions
What usually accompanies the decay of a radioactive nucleus?
Formation of a new nucleus, emission of a particle, and often emission of a gamma ray
Which type of radioactive particle consists of two protons and two neutrons?
Alpha particle
Which type of radioactivity is the most penetrating?
Gamma rays
Which statement about radioactive decay is true?
It is random and spontaneous
What results from the transformation of a neutron into a proton?
Emission of a beta particle
What differentiates natural radioactivity from artificial radioactivity?
Natural radioactive nuclei are found in nature
Study Notes
Structure of an Atomic Nucleus
- A nucleus is represented by the symbol X, where X is the chemical symbol of the element.
- A nucleus consists of protons, neutrons, and electrons.
- The number of protons (Z) is equal to the atomic number, which determines the element of an atom.
- The number of neutrons (N) is equal to the mass number (A) minus the atomic number (Z).
Isotopes
- Two nuclei are isotopes if they have the same number of protons (Z) but a different number of neutrons (N).
- Isotopes have the same atomic number but different mass numbers.
Stability and Instability of Nuclei
- Forces within a nucleus:
- Electromagnetic repulsive forces between protons.
- Strong nuclear forces between nucleons (protons and neutrons).
- Some nuclei are stable, while others are unstable and can undergo radioactive decay.
- The stability of a nucleus depends on the number and type of nucleons it contains.
Radioactivity
- Radioactivity is a process in which unstable nuclei emit radiation to become stable.
- Radioactive decay involves the emission of alpha, beta, or gamma radiation.
- Alpha particles are composed of two protons and two neutrons.
- Beta particles are high-energy electrons emitted from the nucleus.
- Gamma radiation is high-energy electromagnetic radiation.
- Radioactivity is a natural process, but it can also be induced artificially.
Different Types of Radioactivity
- Alpha decay: emission of an alpha particle from the nucleus.
- Beta decay: emission of a beta particle from the nucleus.
- Gamma decay: emission of gamma radiation from the nucleus.
Laws of Conservation
- During a nuclear reaction, the number of protons and neutrons is conserved.
- The total number of protons and neutrons before the reaction is equal to the total number of protons and neutrons after the reaction.
Nuclear Reactions
- Spontaneous nuclear reactions: radioactive decay.
- Induced nuclear reactions: fission and fusion reactions.
- Fission: a heavy nucleus splits into two or more lighter nuclei.
- Fusion: two or more light nuclei combine to form a heavier nucleus.
Applications of Radioactivity
- Medical applications: diagnostic techniques (scintigraphy and tomography), cancer treatment (radiotherapy).
- Scientific applications: exploration of the Earth and its history.
- Energy production: nuclear power plants.
Dangers of Radioactivity
- Ionizing radiation can cause harm to living organisms.
- Radioactive materials can contaminate the environment and pose health risks.
- Exposure to radiation can increase the risk of cancer and other health problems.
Learn about the characteristics of a nucleus, including the number of protons, neutrons, and nucléons. Understand the symbols and formulas used to represent a nucleus.
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