Ionizing Radiation and Nuclear Composition

Ionizing Radiation

• Ionizing radiation consists of high-energy subatomic particles or electromagnetic waves capable of stripping electrons from atoms or molecules.
• Types of ionizing radiation include alpha particles, beta particles, gamma rays, neutrons, and X-rays.
• Radioactivity is the spontaneous disintegration of atomic nuclei, releasing particles or electromagnetic energy.

Nuclear Composition

• The nucleus of an atom comprises protons (positive charge) and neutrons (no charge).
• The mass of a proton (mp = 1.672 x 10^-27 kg) is about 1840 times greater than the mass of an electron (me = 9.11 x 10^-31 kg).
• The mass of a neutron (mn = 1.675 x 10^-27 kg) is slightly smaller than the mass of a proton.
• A nuclide is an atom with a specific number of protons (Z) and neutrons (N).
• Isotopes are atoms of the same element (same Z) but with different numbers of neutrons (A).

Radioactivity

• Stable nuclei have a neutron-to-proton ratio (N/Z) close to 1.
• Unstable nuclei have N/Z greater than 1.
• Electron capture occurs when an unstable nucleus captures an electron from its inner shell, transforming a proton into a neutron and emitting a neutrino.
• Beta decay occurs when a neutron in an unstable nucleus transforms into a proton, releasing an electron (beta particle) with a varying energy range and a neutrino.
• Gamma radiation is electromagnetic radiation emitted during energy transitions within an excited nucleus, not changing the nucleus's composition (Z and A).
• Isomeric transformation involves the transition of a nucleus from an excited state to a ground state, releasing gamma radiation.
• Annihilation occurs when a positron and an electron collide, releasing their energy in the form of two photons.

Law of Radioactive Decay

• The law of radioactive decay quantifies the decrease in the number of radioactive nuclei over time.
• The decay constant (λ) represents the fraction of nuclei that decay per second.
• The half-life (T1/2) is the time required for half of the radioactive nuclei in a sample to decay.
• The relationship between half-life and the decay constant is: T1/2 = ln2/λ.
• The activity of a radioactive source is the number of nuclei decaying per second, measured in becquerels (Bq), where 1 Bq = 1 decay/s.

X-rays

• X-rays are electromagnetic radiation produced when electrons are decelerated by a material.
• X-rays are generated in X-ray tubes, where electrons accelerated by a voltage interact with a metal anode to produce bremsstrahlung and characteristic radiation.
• Bremsstrahlung X-rays are produced when electrons lose energy without exceeding the ionization energy of the material.
• Characteristic X-rays are produced when electrons have enough energy to ionize atoms in the target material.
• The quality of X-ray radiation relates to its energy spectrum, including its "hardness" (average energy) and the number of photons.
• Factors influencing the quality of X-ray radiation include the target material (Z), acceleration voltage (U), anode current (I), exposure time (t), and filtration.

Interaction of Ionizing Radiation with Matter

• Ionizing radiation interacts with matter through various mechanisms, including ionization, excitation, scattering, and absorption.
• Directly ionizing radiation interacts directly with atoms to cause ionization (alpha and beta particles).
• Indirectly ionizing radiation interacts indirectly through secondary electrons (gamma rays and neutrons).
• The linear range of a particle represents the distance it travels in a material before losing all its kinetic energy.
• The penetration depth of ionizing radiation in a material depends on the particle energy, mass, charge, and material properties.

Interaction of Alpha Particles

• Alpha particles interact with matter primarily through collisions with atomic nuclei and electrons, leading to scattering and ionization.

Interaction of Electrons

• Electrons interact with matter by ionizing atoms, exciting electrons, decelerating to emit X-rays, and undergoing nuclear interactions.

Interaction of Positrons

• Positrons interact with matter mainly through annihilation with electrons, releasing their energy as photons.

Interaction of Photons

• Photons interact with matter through various processes, including coherent scattering, the photoelectric effect, Compton scattering, pair production, and photonuclear reactions.
• Coherent scattering occurs when photons interact with atoms without energy loss.
• The photoelectric effect involves the absorption of a photon by an atom, ejecting an electron.
• Compton scattering occurs when a photon interacts with an electron, transferring some energy to the electron, resulting in a scattered photon with lower energy.
• Pair production occurs when a high-energy photon interacts with the electric field of a nucleus, creating an electron-positron pair.
• Photonuclear reactions involve interactions between photons and atomic nuclei, potentially resulting in nuclear disintegration or the emission of neutrons or other particles.

Ionizing Radiation

• Ionizing radiation consists of subatomic particles or electromagnetic waves with enough energy to detach electrons from atoms or molecules.
• Ionizing radiation can be classified into different types: alpha, beta, gamma, and neutrons.

Natural Ionizing Radiation

• Radioactivity is a spontaneous nuclear disintegration that releases elementary particles and electromagnetic waves.

Nuclear Composition

• The nucleus of an atom is composed of protons and neutrons.
• The mass of a proton is 1.672 x 10^-27 kg, which is 1840 times greater than the mass of an electron (9.11 x 10^-31 kg).
• The mass of a neutron is slightly smaller than the mass of a proton (1.675 x 10^-27 kg).
• Nuclides have a unique atomic number (Z) and mass number (A).
• Isotopes have the same atomic number (Z) but different mass numbers (A).

Stable and Unstable Nuclei

• Stable nuclei have a neutron-to-proton ratio (N/Z) close to 1 or have a magic number of protons, neutrons, or protons plus neutrons.
• Unstable nuclei have a neutron-to-proton ratio (N/Z) greater than 1.

Radioactivity

• Unstable nuclei decay into more stable nuclei by releasing particles or electromagnetic waves.
• Alpha decay releases an alpha particle (⁴He nucleus).
• Beta decay releases electrons (beta negative decay), positrons (beta positive decay), or captures an electron (electron capture).
• Gamma decay releases gamma quanta, which are high-energy photons.
• The energy released during radioactive decay is determined by the difference in the rest mass of the initial and final nuclei.

Alpha Decay

• Observed only for nuclei with Z > 82 (elements beyond lead in the periodic table).
• Alpha particles have kinetic energies between 4 and 8.7 MeV.
• The speed of alpha particles is tens of thousands of km/s.

Beta Decay

• Types of beta decay include beta negative, beta positive, and electron capture.
• Beta particles have energies ranging from hundreds of keV to tens of MeV.
• Beta particles have speeds close to the speed of light.

Gamma Radiation

• Gamma radiation is electromagnetic radiation released during the transition of an excited nucleus to a lower energy level.
• The energy of gamma photons is usually between 0.01 and 5 MeV.

Law of Radioactive Decay

• The rate of radioactive decay is proportional to the number of radioactive nuclei present.
• The decay constant (λ) indicates the fraction of radioactive nuclei that decay in 1 second.

Quality of X-ray Radiation

• X-ray radiation is characterized by hardness (quality), number of photons (quantity), and exposure dose.
• Factors that affect the quality, quantity, and dose of X-ray radiation include the target material (Z), acceleration voltage (U), anode current (I), exposure time (t), and flux filtering.

Interaction of Ionizing Radiation with Matter

• Ionizing radiation interacts with matter through direct ionization (alpha, beta particles) or indirect ionization (gamma radiation, neutrons).
• Important characteristics for medical application include linear stopping power (energy loss), ionizing capacity, Bragg's peak, and linear range (penetration).

Linear Range

• The distance a particle travels in a material before losing its kinetic energy depends on the particle's energy, mass, charge, and material properties.
• The linear range of gamma and X-rays depends on scattering and absorption processes.

Interaction of Alpha particles with Matter

• Alpha particles can interact with nuclei (scattering with or without energy change, alpha particle absorption) and electrons (ionization, excitation).

Interaction of Electrons with Matter

• Electrons can emit X-rays, cause impact ionization, and interact with atomic nuclei (nuclear excitation, nuclear decay).

Interaction of Positrons with Matter

• Positrons annihilate with electrons upon slowing down, releasing their energy as two photons.

Interaction of Photons with Matter

• The interaction of photons with matter depends on their energy and involves coherent scattering, photoelectric effect, Compton scattering, pair production, and photonuclear reactions.

Ionizing Radiation

• Ionizing radiation consists of subatomic particles or electromagnetic waves.
• These particles and waves have enough energy to ionize atoms or molecules by detaching electrons.
• When atoms lose an electron they become ions.

Types of Ionizing Radiation

• Alpha Radiation: Emits alpha particles (helium nuclei, 2 protons and 2 neutrons)
• Beta Radiation: Emits beta particles (electrons or positrons)
• Gamma Radiation: Emits gamma rays (high-energy electromagnetic radiation)
• X-rays: Electromagnetic radiation with wavelengths shorter than those of visible light.

Radioactivity

• Radioactivity is a spontaneous disintegration of the nucleus of an atom that releases energy.
• Radioactivity is based on the instability of certain nuclei, which decay into different isotopes.

Nuclear Composition

• Proton: Positively charged particle found in the nucleus of an atom, its symbol is p.
• Neutron: A neutral particle found in the nucleus of an atom, its symbol is n.
• The mass of a proton is 1.672 × 10^-27 kg.
• The mass of a neutron is 1.675 × 10^-27 kg.

Nuclide

• Represented by ZX.
• Z is the atomic number (number of protons).
• A is the mass number (number of protons and neutrons).
• X is the element symbol.

Isotopes

• Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.
• Example of an isotope of carbon: 12C and 14C

Stable Nuclei

• Ratio between the number of neutrons (N) and protons (Z) is close to 1: N/Z≈1.
• May have a "Magic Number" of protons, neutrons, or the sum of protons and neutrons; Magic numbers are 2, 8, 20, 50, and 82.

Unstable Nuclei

• Ratio between the number of neutrons (N) and protons (Z) is greater than 1: N/Z>1.
• Have high amounts of energy and are unstable.
• They will decay to more stable forms.

Radioactive Decay

• Steps:*
• Unstable nuclei spontaneously transform into other nuclei.
• This process is accompanied by the emission of particles or electromagnetic radiation.
• Erest (initial) > Erest (after decay)
• The difference between the initial energy and the final energy is released as kinetic energy.

Types of Radioactive Decay

• Alpha Decay: Emission of an alpha particle (42He).
• Beta Decay:
  • Beta-Minus Decay: Emission of an electron (e-)
  • Beta-Plus Decay: Emission of a positron (e+).
  • Electron Capture: An atomic electron is absorbed by the nucleus, a neutron transforms into a proton, and a neutrino is emitted.
• Gamma Decay: Emission of a gamma ray photon.

Alpha Decay

• Observed only for nuclei with Z > 82 (isotopes that lie behind Pb in the periodic table of elements).
• Alpha particles have a relatively narrow range of kinetic energy of 4 to 8.7 MeV.
• Alpha particles are emitted at speeds of tens of thousands of km/s.

Beta Negative Decay

• Occurs in isotopes with a relatively high number of neutrons.

Beta Positive Decay

• Occurs in isotopes with a relatively low number of neutrons.

Law of Radioactive Decay

• N(t) = N0e^(-λt)
• N(t) is the number of radioactive nuclei at time t.
• N0 is the initial number of radioactive nuclei.
• λ is the decay constant.

Half-life

• T1/2 = ln2 /λ
• T1/2 is the half-life of a radioactive isotope.
• It is the time required for the number of radioactive nuclei to decrease by half.

Activity

• A = -dN/dt
• A is the activity of the radioactive source.
• A is the average number of decays per second, expressed in Becquerel (Bq).

X-Rays

• Electromagnetic radiation with wavelengths shorter than those of visible light.
• Wavelengths range from 0.01 to 10 nanometers.

X-Ray Tube

• X-rays are produced by bombarding a metal target with a beam of high-energy electrons.
• Electrons interact with the target atoms and produce X-rays.

Types of X-rays

• Bremsstrahlung X-rays:
  • Produced when electrons are decelerated by the electric field of the target atoms.
  • The emitted X-rays have a continuous spectrum.
• Characteristic X-rays:
  • Produced when electrons transition between energy levels in the target atoms.
  • The emitted X-rays have specific wavelengths.

Bremsstrahlung

• The energy (hν) of the emitted X-rays depends on the kinetic energy of the electron.
• The maximum energy of the Bremsstrahlung X-rays is equal to the kinetic energy of the incident electron.

Interaction of Ionizing Radiation with Matter

• Alpha Particles: Interact with matter through scattering, ionization and excitation processes.
• Electrons: Interact with matter through scattering, ionization and excitation processes.
  • May emit X-rays when stopped.
• Positrons: Undergo annihilation with electrons when an electron stops.
  • The annihilation process produces two photons.
• Photons: Interact with matter through coherent scattering, photoelectric effect, Compton scattering, pair production, and photonuclear reactions.
  • The type of interaction depends on the energy of the photon.

Coherent Scattering

• A photon interacts with an atom as a whole.
• It results in a change in direction of the photon, but no energy is transferred.
• Also known as Rayleigh scattering or Thompson scattering.

Photoelectric Effect

• A photon is absorbed by an atom, causing an electron to be ejected.
• The energy of the photon is equal to the binding energy of the electron plus the kinetic energy of the ejected electron.

Compton Scattering

• A photon interacts with an electron, resulting in a change in direction and energy of the photon.
• The energy of the photon is transferred to the electron.
• The Compton Effect is an important source of scattered radiation in diagnostic and therapeutic radiology.

Pair Production

• A photon interacts with the nucleus of an atom, creating a pair of particles: an electron and a positron.
• This process occurs when the energy of the photon is greater than 1.022 MeV, which is the rest mass energy of the electron-positron pair.

Photonuclear Reactions

• A photon interacts with the nucleus of an atom, causing nuclear excitation or even nuclear disintegration.
• High energy photons are required for these reactions.
• The interaction results in nuclear transmutations, releasing energetic particles such as neutrons, protons, and alpha particles.

Ionizing Radiation Safety

• Ionizing radiation is harmful and can cause health problems.
• Minimize exposure to ionizing radiation by:
  • Reducing time of exposure.
  • Increasing the distance from the source.
  • Using shielding to block the radiation.
• Follow all safety procedures and regulations for handling and using ionizing radiation.

Ionizing Radiation

• Ionizing radiation consists of subatomic particles or electromagnetic waves with enough energy to detach electrons from atoms or molecules.

Types of Ionizing Radiation

• Alpha particles, beta particles, gamma rays, x-rays, neutrons

Natural Ionizing Radiation and Radioactivity

• Radioactivity is the spontaneous disintegration of nuclei with the release of elementary particles or electromagnetic waves.

Nuclear Composition

• Proton: positively charged particle with a mass of 1.672 x 10^-27 kg.
• Neutron: neutral particle with a mass of 1.675 x 10^-27 kg.
• The mass of a proton is 1840 times greater than an electron.

Nuclides

• A nuclide is a specific atom characterized by its atomic number (Z) and mass number (A).

Isotopes

• Isotopes are atoms of the same element (same atomic number) that have different mass numbers due to a different number of neutrons.

Radioactivity

• Stable nuclei have an N/Z ratio close to 1 or have a magic number of protons, neutrons, or the sum of both.
• Unstable nuclei have an N/Z ratio higher than 1 and may undergo radioactive decay.
• Radioactive decay releases energy which is greater than the initial rest energy of the nucleus.

Types of Radioactive Decay

• Alpha decay: nucleus emits an alpha particle (Helium nucleus)
• Beta decay: nucleus emits a beta particle (electron or positron)
• Gamma decay: nucleus emits a gamma ray (high-energy photon)

Alpha Decay

- Alpha decay occurs in nuclei with atomic numbers greater than 82.
- Alpha particles are released with energies of 4 to 8.7 MeV, corresponding to speeds of thousands of km/s.

Beta Decay

• Beta-minus decay: neutron decays into a proton, an electron, and an antineutrino.
• Beta-plus decay: proton decays into a neutron, a positron, and a neutrino.
• Electron Capture: electron is captured by the nucleus, combining with a proton to form a neutron and a neutrino.

Gamma Radiation

• Gamma radiation occurs when an excited nucleus transitions to a lower energy level.
• Gamma photons have energies ranging from 0.01 to 5 MeV.

Bremsstrahlung

• Bremsstrahlung occurs when an electron is decelerated by the Coulomb forces of atomic nuclei.
• It is a continuous spectrum of X-ray radiation ranging from low energy to the maximum energy of the electron.
• The maximum energy of bremsstrahlung photons is equal to the kinetic energy of the electron.

Characteristic X-ray

• Characteristic X-ray radiation is emitted when an electron transitions from a higher to a lower energy level in an atom.
• The emitted X-rays have specific energies corresponding to the energy differences between those electron shells.

Law of Radioactive Decay

• The rate of decay of radioactive nuclei is proportional to the number of nuclei present.
• The decay constant λ represents the fraction of nuclei that decay per unit time.

This quiz covers fundamental concepts related to ionizing radiation, including its types such as alpha and beta particles, and the basics of nuclear composition involving protons and neutrons. Explore the definitions of nuclides, isotopes, and the principles of radioactivity. Test your understanding of how atomic structure influences stability and radioactivity.