Nuclear Chemistry: Radioactivity

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Atomic nuclei are made up of Protons and Neutrons
Protons and neutrons are collectively called nucleons
Nuclide
An atom in nuclear chemistry, identified by the number of protons and neutrons in the nucleus
How to identify a nuclide
1. Name of element and mass number (nucleons in nucleus)
How to identify a nuclide
2. Isotopic symbol
Which atoms undergo radioactive decay?
Atoms that are isotopes with unstable nuclei
Radioisotopes
Isotopes with an unstable nuclei, all nuclides with the atomic # over 83
Radioactive decay
Spontaneous disintegration of a nucleus into a slightly lighter nucleus accompanied by the emission of particles, electromagnetic radiation, or both
Nuclear radiation
particles or electromagnetic radiation that is emitted from the nucleus during radioactive decay
Half-time
Amount of time taken for half of the atoms of a radioactive nuclide to decay (t•1/2)
What does a nuclide’s type and rate of decay depend on?
Nucleon’s content and energy levels
Types of radioactive decay
1. Alpha Emission
2. Beta Emission
3. Position Emission
4. Gamma Emission
Alpha Emission
-emitted from the nucleus
-2 protons and 2 neutrons bound together
-all a helium charged atom of +2
-both protons and neutrons must be emitted to achieve stability
-least amount of penetrating ability
Beta Emission
-occurs bc elements have too many neutrons
-to reduce the number of neutrons, a neutron is converted into a proton and an electron
-a beta particle is the electron and is emitted from the nucleus
-beta particles are ab 100 times more penetrating than alpha particles
-can penetrate ab 1-2 mm into material and damage skin
Position Emission
-sometimes an atom has too many protons to be stable
-protons can be converted to a neutron by emitted a positron
-positrons are particles the have the same mass as electrons but have positive charges
Gamma Emission
-gamma radiation usually occurs immediately following other types of decay when the nucleus is still in an excited state
-gamma rays are high energy electromagnetic waves emitted from a nucleus as it changes from an excited states to a ground state
-gamma rays are highly penetrating and can go deep into solid materials
-cause deep tissue damage and only stopped by heavy shielding
Roentgen
Unit used to measure nuclear radiation, it is equal to the amount of radiation that produces 2×10 to the ninth ion pairs when it passes through 1 cc of dry air
1 Rem =
The quantity of ionizing radiation that does as much damage to human tissue as is done by 1 roentgen of high voltage x-rays
Average exposure of radiation in US
0.1 rem/year
How many commonly used devices for detecting radiation are there?
3
What are the 3 devices for detecting radiation?
Geiger Muller Counter, Scintillation Coutner, Film Badge
Geiger Muller counter
instruments that detect radiation by counting electric pulses carried by gas ionized by radiation (mostly beta detection)
Scintillation Counter
scintillation counters are instruments that convert scintillating light to an electric signal for detecting radiation
Film Badges
use exposure of film to measure the approx. amount of radiation a person undergoes when in certain environments
Categories: Nuclear Chemistry