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22.2 Nuclear Forces and Radioactivity

3 min read•june 25, 2024

Nuclear forces shape the atomic world, governing interactions between subatomic particles. Strong and weak nuclear forces, along with electromagnetic forces, determine nuclear stability. Understanding these forces is crucial for grasping the behavior of atomic nuclei and their energy potential.

Radioactive decay occurs when unstable atomic nuclei release energy through radiation. Alpha, beta, and have distinct properties and effects. Decay equations describe these processes mathematically, helping us predict and analyze nuclear transformations in various applications.

Nuclear Forces and Interactions

Forces within atomic nuclei

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- Attracts quarks within protons and neutrons
- Exchanged by gluons, the strongest fundamental force
- Acts only within the nucleus due to its short range
- Repels protons because of their positive charges
- Follows Coulomb's law: $F = k \frac{q_1 q_2}{r^2}$ ( $k$ : Coulomb's constant, $q_1$ , $q_2$ : particle charges, $r$ : distance)
- Weaker than the strong force inside the nucleus but has a longer range
- Responsible for certain types of radioactive decay, such as beta decay
- Much weaker than the strong nuclear force and electromagnetic force
- Quantifies the energy needed to separate a nucleus into protons and neutrons
- Indicates nuclear stability
- Determined by the : $\Delta E = \Delta m c^2}$ ( $\Delta E$ : binding energy, $\Delta m$ : mass defect, $c$ : light speed)

Radioactive Decay and Radiation

Types of nuclear radiation

Alpha ( $\alpha$ $α$ ) radiation
- Made of helium-4 nuclei (2 protons, 2 neutrons)
- Strongly ionizing but weakly penetrating
- Blocked by paper or skin
- Damages living tissue if inhaled or ingested (radon gas)
Beta ( $\beta$ $β$ ) radiation
- Consists of energetic electrons ( $\beta^-$ ) or positrons ( $\beta^+$ )
- Moderately ionizing and penetrating
- Stopped by thin aluminum or plastic (safety goggles)
- Penetrates skin and harms living tissue (radiation burns)
Gamma ( $\gamma$ $γ$ ) radiation
- High-energy photons in the electromagnetic spectrum
- Weakly ionizing but highly penetrating
- Blocked by thick lead or concrete (nuclear reactor shielding)
- Damages living tissue even from a distance (cancer risk)
radiation
- Consists of free neutrons, often produced in reactions
- Highly penetrating and can induce radioactivity in other materials

Equations for radioactive decay

: $^A_Z X \rightarrow ^{A-4}_{Z-2} Y + ^4_2 He$ $_{Z}^{A} X \to_{Z - 2}^{A - 4} Y +_{2}^{4} He$
- Parent nucleus $X$ forms daughter nucleus $Y$ and an alpha particle ( $^4_2 He$ )
- Mass number $A$ reduces by 4, atomic number $Z$ reduces by 2 (uranium-238 to thorium-234)
: $^A_Z X \rightarrow ^A_{Z+1} Y + e^- + \bar{\nu}_e$ $_{Z}^{A} X \to_{Z + 1}^{A} Y + e^{-} + \overset{ν}{ˉ}_{e}$
- Neutron in parent nucleus $X$ becomes a proton, emitting an electron ( $e^-$ ) and ( $\bar{\nu}_e$ )
- Mass number $A$ stays constant, atomic number $Z$ increases by 1 (carbon-14 to nitrogen-14)
: $^A_Z X \rightarrow ^A_{Z-1} Y + e^+ + \nu_e$ $_{Z}^{A} X \to_{Z - 1}^{A} Y + e^{+} + ν_{e}$
- Proton in parent nucleus $X$ becomes a neutron, emitting a ( $e^+$ ) and ( $\nu_e$ )
- Mass number $A$ stays constant, atomic number $Z$ decreases by 1 (potassium-40 to argon-40)
: $^A_Z X^* \rightarrow ^A_Z X + \gamma$ $_{Z}^{A} X^{*} \to_{Z}^{A} X + γ$
- Excited nucleus $X^*$ emits a gamma photon ( $\gamma$ ) to reach a lower energy state
- Mass number $A$ and atomic number $Z$ remain unchanged (technetium-99m in medical imaging)

Nuclear Reactions and Decay Rates

Nuclear fission: The splitting of heavy atomic nuclei into lighter nuclei, releasing energy and neutrons
: The combining of light atomic nuclei to form heavier nuclei, releasing large amounts of energy
: The time required for half of the atoms in a sample of a radioactive isotope to decay

Key Terms to Review (21)

Alpha Decay: Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle, consisting of two protons and two neutrons. This process results in the transformation of the parent nucleus into a daughter nucleus with a lower atomic number.

Alpha Radiation: Alpha radiation is a type of ionizing radiation consisting of high-energy alpha particles, which are the nuclei of helium atoms. It is one of the three main types of radioactive decay, along with beta radiation and gamma radiation.

Beta Minus Decay: Beta minus decay is a type of radioactive decay where a neutron in the nucleus of an atom is converted into a proton, an electron, and an antineutrino. This process results in the emission of a high-energy electron, known as a beta particle, from the nucleus.

Beta Plus Decay: Beta plus decay is a type of radioactive decay in which a proton in the nucleus of an atom is converted into a neutron, emitting a positron (the antiparticle of an electron) and a neutrino. This process occurs in certain unstable nuclei with an excess of protons, and it is a way for the nucleus to become more stable by reducing its proton-to-neutron ratio.

Beta Radiation: Beta radiation is a type of ionizing radiation emitted from the nucleus of certain radioactive atoms during the process of beta decay. It consists of high-energy electrons or positrons that are ejected from the nucleus with significant kinetic energy.

Binding Energy: Binding energy is the amount of energy required to separate a nucleus into its individual protons and neutrons. It represents the force that holds the nucleus together and is a crucial concept in understanding nuclear forces and radioactivity, as well as nuclear fission and fusion processes.

Electromagnetic Force: The electromagnetic force is a fundamental force of nature that arises from the interaction between electrically charged particles. It is responsible for a wide range of phenomena, including the attraction and repulsion between charged objects, the generation of electric and magnetic fields, and the propagation of electromagnetic radiation.

Electron Antineutrino: An electron antineutrino is a subatomic particle that is the antiparticle of the electron neutrino. It is an electrically neutral, weakly interacting lepton that is produced in certain nuclear processes, such as beta decay.

Electron Neutrino: The electron neutrino is an electrically neutral, weakly interacting elementary particle that is one of the three types of neutrinos, along with the muon neutrino and tau neutrino. It is a fundamental particle in the Standard Model of particle physics and plays a crucial role in understanding nuclear forces and radioactivity.

Gamma Emission: Gamma emission is a type of radioactive decay process in which a nucleus releases excess energy in the form of high-energy electromagnetic radiation known as gamma rays. This occurs when an atomic nucleus transitions from a higher energy state to a lower energy state, shedding the excess energy through the emission of a gamma photon.

Gamma Radiation: Gamma radiation is a type of electromagnetic radiation with the highest energy and shortest wavelength in the electromagnetic spectrum. It is produced by the radioactive decay of atomic nuclei and has the ability to penetrate deeply into matter, making it a powerful and potentially hazardous form of radiation.

Gluon: A gluon is a fundamental force carrier particle that is responsible for the strong nuclear force, which binds together the quarks that make up hadrons like protons and neutrons. Gluons mediate the interactions between quarks, holding the particles together within the nucleus of an atom.

Helium-4 Nucleus: The helium-4 nucleus, also known as the alpha particle, is the nucleus of the helium-4 atom, which is the most stable isotope of helium. It consists of two protons and two neutrons, making it the simplest atomic nucleus after the hydrogen-1 nucleus.

Mass Defect: Mass defect is the difference between the total mass of the individual protons and neutrons in an atomic nucleus and the actual mass of the nucleus. This difference in mass is a result of the binding energy that holds the nucleus together.

Neutron: A neutron is an electrically neutral subatomic particle that is a fundamental constituent of atomic nuclei, along with protons. Neutrons play a crucial role in the stability and properties of atoms, as well as in various physical and nuclear processes.

Nuclear Fission: Nuclear fission is the process of splitting heavy atomic nuclei, such as uranium or plutonium, into lighter nuclei. This process releases a large amount of energy and is the basis for nuclear power generation and nuclear weapons.

Nuclear Fusion: Nuclear fusion is the process in which two or more atomic nuclei collide at high speeds and combine to form a new, heavier nucleus. This process releases a large amount of energy, making it a potential source of power for the future.

Positron: A positron is the antimatter counterpart of the electron, with the same mass but a positive electric charge. It is a fundamental particle that plays a crucial role in the understanding of nuclear forces and radioactivity.

Radioactive Half-Life: Radioactive half-life is the time it takes for a radioactive substance to lose half of its radioactivity through the process of radioactive decay. It is a fundamental concept in understanding the behavior and applications of radioactive materials.

Strong Nuclear Force: The strong nuclear force is one of the four fundamental forces in nature, along with gravity, electromagnetism, and the weak nuclear force. It is the force that binds protons and neutrons together in the nucleus of an atom, overcoming the repulsive electromagnetic force between the positively charged protons. This force is incredibly powerful, acting over extremely short distances within the atomic nucleus, and is responsible for the stability of atomic nuclei.

Weak Nuclear Force: The weak nuclear force is one of the four fundamental forces in nature, along with gravity, electromagnetism, and the strong nuclear force. It is responsible for certain types of radioactive decay, such as beta decay, and plays a crucial role in the stability of atomic nuclei and the interactions within them.

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Practice QuizGlossary

Practice Quiz Glossary

22.2 Nuclear Forces and Radioactivity

Nuclear Forces and Interactions

Forces within atomic nuclei

Top images from around the web for Forces within atomic nuclei

Top images from around the web for Forces within atomic nuclei

Radioactive Decay and Radiation

Types of nuclear radiation

Equations for radioactive decay

Nuclear Reactions and Decay Rates

Key Terms to Review (21)

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AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.

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