Nuclear Chemistry
Nuclear Chemistry
Involves changes in the nucleus of an atom.
Three types of Nuclear Chemistry
1. Radioactive decay
2. Fission
3. Fusion
2. Fission
3. Fusion
Isotopes
A version of an atom with a different number of neutrons. You can write an isotope by writing the element abbreviation, and on the top left side have the mass number. On the low left side, you would put the number of protons, which is also the atomic number.
Isotopes with hyphens
To write an isotope using hyphens, simply write the element abbreviation, then next to a hyphen on the right side, write the mass number.
Radioactive decay
Process by which an unstable nucleus emits particles and energy to change into a different, more stable atom.
Types of Radioactive decay
Alpha, Beta, Gamma
Alpha decay (α)
Emits two protons and two neutrons in the form of a Helium atom. So, it causes the atomic number to decrease by two, and the mass number to decrease by four.
Beta decay (β)
Emits one electron, and the proton stays in the atom causing the atomic number to increase by one. With beta decay, there is no change in the mass number.
Gamma decay (γ)
Produced by the unstable nucleus, and happens along with α and β decay. NOT particles, but a photon of energy. Does not change mass, or atomic number.
Penetrating power for Alpha, Beta, and Gamma decay
Alpha particles have the least penetrating power; your hand can stop it. Beta particles can be stopped by a thin sheet of aluminum, and Gamma particles can be stopped by a thick sheet of lead.
Nuclear Energy
Results in large amounts of energy being released. The two types are fission, and fusion.
Fission
A stable isotope strikes a stable isotope causing it to become unstable, and split apart.
Fusion
Process in which small nuclei join together to make a larger nuclei. Takes place in the sun, or in the core of every star.
Half-Life
Time it takes for one-half of the atoms of a radioactive isotope (parent) to emit radiation, and decay to its products (daughter).
Positron
(Also known as Beta plus decay)
– proton inside nucleus is converted into neutron.
– releases a positron, and an electron neutrino.
– Atomic number goes down by one, and mass number stays the same.
– proton inside nucleus is converted into neutron.
– releases a positron, and an electron neutrino.
– Atomic number goes down by one, and mass number stays the same.
Electron Capture
– Proton converts to a neutron because an electron fell into the nucleus.
– Releases a neutrino
– Atomic number decreases by one.
– No change in mass number.
– Releases a neutrino
– Atomic number decreases by one.
– No change in mass number.
Why are some isotopes stable and some radioactive?
It depends on the proton to neutron ratio. Ratio above band of stability:
Atomic number < 83 = beta decay. Atomic number ≥ 83 = Alpha decay. Ratio below band of stability: positron emission or electron capture.
Atomic number < 83 = beta decay. Atomic number ≥ 83 = Alpha decay. Ratio below band of stability: positron emission or electron capture.