7.1 Discrete energy and radioactivity

Atomic Physics

The branch of physics that deals with the structure and properties of atoms, focusing on the nucleus, electrons, and energy levels.

Nuclear Physics

The field of physics that studies atomic nuclei and their interactions, including nuclear reactions and radioactivity.

Nucleus

The central part of an atom that contains protons and neutrons, with a positive charge.

Electrons

Negatively charged particles that orbit the nucleus of an atom in fixed orbits.

Protons

Positively charged particles found in the nucleus of an atom.

Neutrons

Uncharged particles located in the nucleus of an atom.

Energy Levels

Specific orbits around the nucleus where electrons are restricted to occupy in an atom, each corresponding to a different amount of energy.

Hydrogen Atom

The simplest element, consisting of a proton bound to a single electron by the electromagnetic force.

Isotopes

Atoms of the same element with different numbers of neutrons in the nucleus.

Planetary Model

A visualization of the atom where the electron orbits the nucleus similar to planets orbiting the sun.

Quantum Mechanics

The branch of physics that deals with the behavior of particles at the atomic and subatomic levels, explaining phenomena like energy levels and electron behavior.

Charge

A property of matter that can be positive or negative, leading to interactions through electromagnetic fields.

Electromagnetic Field

A field that describes the interactions between charged particles, such as protons and electrons, at a distance.

Energy Levels

Different states of energy that an electron can occupy within an atom, typically represented diagrammatically.

Ground State

The lowest energy level an electron can occupy in an atom, considered the most stable state.

Excited State

When an electron occupies an energy level higher than the ground state, it is said to be in an excited state.

Quantized

Energy levels in atoms are quantized, meaning they can only have discrete finite values.

Photon

A packet or quantum of light energy that can be absorbed by an atom to excite electrons to higher energy levels.

Planck Constant

Denoted by 'h', a fundamental constant in quantum mechanics used to relate the energy of a photon to its frequency.

Wavelength

The distance between successive crests of a wave, in the context of photons, it is related to the energy and frequency of the radiation.

Electron Volt (eV)

A unit of energy commonly used in atomic physics, where 1 eV is equivalent to 1.6 × 10^-19 joules.

Principal Quantum Number (n)

Denoted by 'n', it represents the energy level of an electron in an atom, with higher values corresponding to higher energy levels.

Ionization Energy

The energy required to remove an electron completely from an atom, resulting in the atom becoming ionized.

Singly-ionized helium (He+)

An ionized form of helium that has lost one electron, making it "hydrogen-like" in behavior.

Ground State

The lowest energy state of an atom or molecule.

Photon

A quantum of light or other electromagnetic radiation.

Electromagnetic Spectrum

The range of wavelengths or frequencies over which electromagnetic radiation extends.

Emission Spectra

The spectrum of light emitted by excited atoms or molecules.

Absorption Spectra

The spectrum of light absorbed by atoms or molecules.

Diffraction Grating

A device used to disperse light into its constituent wavelengths.

Fraunhofer Lines

Dark lines in the solar spectrum caused by absorption of specific wavelengths of light by elements in the Sun's atmosphere.

Absorption Spectrum

A continuous spectrum with absorption lines corresponding to the frequencies of light in the emission spectrum of the elements within the substance that is absorbing the light.

Diffraction Grating

A device used to disperse light into its component wavelengths for observation.

Prism

Another device used to disperse light into its component wavelengths for observation.

Photon

A quantum of light; the energy of a photon is directly proportional to its frequency.

Energy Levels

Discrete levels of energy that electrons in an atom can possess.

Radioactive Decay

The process in which an unstable atom changes into a different nuclear configuration by emitting alpha particles, beta particles, or gamma radiation.

Nucleus

The central part of an atom containing protons and neutrons.

Nucleon

A collective term for protons and neutrons in the nucleus of an atom.

Strong Nuclear Force

The force that binds protons and neutrons together in the nucleus, overcoming the electrostatic repulsion between protons.

Nuclide

A distinct atomic nucleus characterized by a specific number of protons and neutrons.

Alpha Particle

A particle emitted during alpha decay, consisting of two protons and two neutrons (essentially a helium nucleus).

Isotope

Nuclides of the same element with the same number of protons but different numbers of neutrons.

Gamma Photon

A high-energy photon emitted during the de-excitation of an excited nucleus.

Beta Emission

The process in which a nucleus decays by emitting a beta particle (electron or positron).

Half-life

The time taken for half of the radioactive nuclei in a sample to decay or for the activity of the sample to decrease by half.

Nuclear Equation

A symbolic representation of a nuclear reaction showing the atomic number and mass number of the particles involved.

Radioactive Decay

The process by which an unstable atomic nucleus loses energy by emitting radiation.

Nucleus

The central part of an atom containing protons and neutrons, with a diameter of about 10^-15 meters.

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons.

Radioactive Isotope

An isotope with an unstable nucleus that undergoes radioactive decay.

Exponential Decay

The type of decay where the rate of decay is proportional to the number of radioactive nuclei present.

Nuclear Interaction

Processes involving collisions or interactions between atomic nuclei.

Geiger-Müller (G-M) tube

A metal cylinder filled with low-pressure gas used to measure beta and gamma radiation by ionizing the gas, producing a pulse of current that can be measured by a counting circuit.

Spark counter

A device used to detect alpha particles, where a spark jumps between a gauze and a filament when alpha particles ionize the air.

Background count

The reading obtained by a Geiger-Müller tube when connected to its counter and switched on, even in the absence of a radioactive source, measuring the natural radiation present in the environment.

Sievert (Sv)

A unit of radiation that considers the ionizing effects of different radiations, with most people absorbing between 1.5 and 3.5 millisievert per year from background radiation.

Absorption of radiation

The interaction of different radioactive emissions with materials based on their ionizing ability, where alpha, beta, and gamma particles require varying thicknesses of materials to be absorbed.

Alpha particles

Positively charged particles that strongly ionize gases, have a short range in air, and are absorbed by thin paper due to their massiveness and charge of +2e.

Beta particles

Negatively charged particles with a range of several centimeters in air, requiring a few millimeters of aluminum for absorption, lighter than alpha particles with a charge of -1e.

Gamma rays

Electromagnetic waves that interact minimally with matter, necessitating many meters of air or several centimeters of lead for absorption.

Ionizing ability

The capability of radioactive emissions to ionize gases or materials, influencing their range and the materials needed for absorption.

Counting circuit

A circuit that measures the pulse of current produced by ionization in a Geiger-Müller tube, used to quantify the radiation detected.

Nuclide

A nuclide is a nucleus with a specific number of protons and neutrons.

Half-life

Half-life is the time required for the count rate to decrease by half in value or for half of the number of nuclei to decay into nuclei of another element.

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.

Beta Decay

Beta decay is a type of radioactive decay in which a beta particle (an electron or positron) is emitted from an atomic nucleus.

Gamma Decay

Gamma decay is a type of radioactive decay in which a gamma ray is emitted from an atomic nucleus.

G-M Tube

A Geiger-Muller (G-M) tube is a device used for detecting ionizing radiation.

Background Count Rate

The average count rate detected by a radiation detector when no radioactive source is present.

Count Rate

The number of radiation counts detected per unit time by a radiation detector.