Atomic and Nuclear Physics Flashcards

Flashcards about Atomic and Nuclear Physics.

Dalton's Atomic Theory:

Elements are made of tiny particles called atoms.

J. J. Thomson’s plum pudding model:

Proposed by J. J. Thomson, the discoverer of the electron in 1897, this model suggests the atom is composed of electrons surrounded by a soup of positive charge, like plums in a pudding.

The Rutherford model:

The atom is made up of a positive nucleus consisting of protons surrounded by a cloud of orbiting electrons.

Atomic Number (Z):

The number of protons (Z).

Mass Number (A):

The number of protons PLUS neutrons (A).

Isotopes:

Atoms of the same element (same atomic number) but with different numbers of neutrons (different mass number).

Radioactivity:

Radioactivity results from the random and spontaneous breakdown of the unstable nucleus of an atom.

Alpha Particle:

Helium nucleus made up of 2 protons & 2 neutrons.

Beta Particle:

High kinetic energy electron

Gamma Radiation:

Very high frequency electromagnetic radiation

Nuclear Equations:

When alpha decay occurs, mass no. decreases by 4 and atomic no. decreases by 2. For beta decay, mass number does not change, atomic number increases by 1. Gamma decay, a gamma ray is released (energy), no change to mass & atomic number.

Transmutation:

In both α and β a new element is formed which is called the transmutation of one element into another.

Making Isotopes:

To “make” radioisotopes for use in industry and medicine, stable isotopes are bombarded with neutrons in a nuclear reactor.

Natural sources of Radioactivity:

radiation from space (cosmic rays from Sun), from naturally occurring radioisotopes in rocks e.g. granite, and radiation due to human activity - atomic weapons testing & emissions from nuclear power stations.

Detection and measurement of Radioactivity:

Geiger-Muller (GM) tube and counter electronically amplifies the ionising effect of the radiation. Photographic film badges (for workers in nuclear industry and hospitals) monitor how much radiation they are exposed to.

Dangers of Radioactivity:

When radioactivity hits living cells, alpha, beta and gamma radiation collides with neutral atoms or molecules, knocking off electrons and turning them into charged/ionised particles (ions).

Uses of Radioactive Isotopes:

Smoke detectors (alpha), monitoring thickness (beta), medical tracers and cancer treatment (gamma).

Nuclear Fission:

When large atomic nuclei are hit with neutrons they can become unstable and breaks into two smaller 'daughter' nuclei and releases more neutrons, (as well as α and β particles and γ). This is nuclear fission and is accompanied by an enormous release of energy.

Nuclear Reactors:

Control rods of boron can be lowered into the reactor core to absorb neutrons and slow down fission to keep the chain reaction under control. Moderator rods slow down the neutrons produced by the chain reaction as slow moving neutrons are needed to bring about further fission.

Nuclear Fusion:

The process by which a heavier atomic nucleus is made from two smaller atomic nuclei.

Half-Life:

Is the time it takes for half of the radioactive atoms in radioactive material to decay.