p4 - atomic structure

Model of the atom

A framework for understanding atomic structure and behavior, developed over time through various experiments.

Dalton’s Atomic Theory (1804)

Proposed that atoms are tiny, indivisible spheres, with each element consisting of a unique type of atom.

J.J. Thompson's discovery

Identified electrons, disproving Dalton's model; introduced the 'plum pudding' model of the atom.

Rutherford's Experiment

Demonstrated the existence of the nucleus by firing alpha particles at gold foil; some particles bounced back.

Nuclear Model (Niels Bohr)

Proposed that electrons orbit the nucleus in defined energy levels.

James Chadwick

Discovered the neutron, explaining discrepancies between atomic numbers and mass numbers.

Ionization

The process of adding or removing electrons from an atom, resulting in the formation of ions.

Isotopes

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

Stable isotopes

Isotopes of an element that do not undergo radioactive decay.

Radioactive decay

The process where unstable isotopes transform into other elements, emitting radiation in the process.

Ionizing radiation

Radiation powerful enough to knock electrons off atoms, creating ions.

Alpha particles

Helium nuclei consisting of 2 protons and 2 neutrons; strongly ionizing but with low penetration.

Beta particles

High-speed electrons released from the nucleus during beta decay; moderately ionizing.

Gamma radiation

Electromagnetic waves emitted by nuclei; weakly ionizing but highly penetrating.

Nuclear equation

An equation that represents radioactive decay processes, balancing atomic and mass numbers.

Alpha decay

A type of decay where an atom emits an alpha particle, reducing its atomic number by 2 and mass number by 4.

Beta decay

A decay process where a neutron is converted into a proton and an electron is emitted.

Gamma decay

A process where excess energy is released from the nucleus without changing atomic or mass numbers.

Half-life

The time required for half of the radioactive nuclei in a sample to decay.

Geiger-Muller tube

An instrument used to measure radiation count rates.

Activity of a source

The rate at which a radioactive source decays, measured in becquerels (Bq).

Contamination

The presence of radioactive particles on or within an object.

Irradiation

Exposure of an object to ionizing radiation without making it radioactive.

Reducing contamination techniques

Using gloves, tongs, and protective suits to handle radioactive materials safely.

Danger of alpha radiation inside the body

Very ionizing but low penetration makes it hazardous if ingested or inhaled.

Danger of beta and gamma radiation outside the body

High penetrating power allows these radiations to reach organs and cause damage.

Penetrating power of gamma radiation

Strong penetrating ability allows gamma rays to pass through tissues easily.

Ionizing power assessment

The measure of how easily radiation can knock off electrons from atoms.

Decay balance in nuclear equations

The atomic and mass numbers must be conserved on both sides of the equation.

Radiation emission types

Includes alpha, beta, and gamma radiation, all produced during radioactive decay.

Neutron in beta decay

A neutron transforms into a proton and an electron is emitted, resulting in an increased atomic number.

Randomness of decay

Radioactive decay occurs randomly, making prediction of individual decay events impossible.

Decay graph interpretation

A graph plotting activity against time allows visualization of half-life and decay patterns.

Lead lining for safety

A common method to reduce exposure to radiation by shielding it.

Proton number in isotopes

The number of protons remains the same in isotopes of a given element.

Short range of alpha particles

Alpha particles have a limited range in air and are absorbed by paper.

Significance of half-life in dating

Half-life helps determine the age of materials by measuring decay rates.

Helium nuclei in alpha particles

Alpha particles are composed of two protons and two neutrons, resembling helium nuclei.