H3 Nuclear Chemistry
The use of nuclear energy to make new materials, radioisotopes, for use in medicine and industry is investigated in this chapter. The chapter looks at the properties of different forms of radiation, nuclear decay and the use of nuclear equations to describe these transmutations.
Radioactivity / The phenomenon of atoms emitting some form of radiation.Radioisotopes / · Also known as radioactive isotopes
· The isotopes of elements that emit radiation.
· All isotopes of radioactive elements emit radiation.
· Unstable nuclei are radioactive
· Stable nuclei are not radioactive
Atomic number (Z) / The number of protons in the nucleus of every atom of that element.
Mass number (A) / The number of protons and neutrons in the nucleus of the species concerned.
Isotopes / · Atoms of the same element that have different numbers of neutrons in the nuclei of the atoms.
· Isotopes have the same atomic number but different mass numbers.
Unstable isotopes / · The atomic number is greater than 83
· The ratio of neutrons to protons places it outside the zone of stability.
Alpha radiation / · Symbols a, 4He2
· Identity helium nucleus
· Relative charge +2
· Relative mass 4
· Penetrating power low
Beta radiation / · Symbols b, 0e-1
· Identity electron
· Relative charge -1
· Relative mass 1/2000
· Penetrating power moderate
Gamma radiation / · Symbols g
· Identity electromagnetic radiation
· Relative charge 0
· Relative mass 0
· Penetrating power high
Nuclear equations / The atomic number is written as a subscript to the left of the symbol and the mass number as a superscript, also to the left.
Nuclear fission / · Also known as splitting the atom
· Involves bombarding the nuclei with neutrons
· The nucleus is split into two equal fragments and neutrons with the release of large amounts of energy.
· A controlled fission reaction occurs in a nuclear reactor.
Transuranic elements / · Elements with mass numbers greater than 92 (uranium)
· Transuranic elements are all artificially made.
Half-life / · The time required for half the atoms in a given sample of a radioisotope to undergo radioactive decay.
· The half-life is independent of the initial mass of the isotope present.
Detection of radiation / · Photographic film
· Cloud chamber
· Geiger-Muller tube
· Scintillation counter
Uses of radioisotopes / · Cancer treatment
· Diagnosis
· Thickness gauges in industry
· Leak detectors in underground pipes
· Irradiation of medical supplies and food
· Scientific research as tracers to determine reaction mechanisms
· Domestic smoke alarms