Nuclear Chemistry Review

Published by admin on

Process by which nuclei of unstable isotopes emit radiation
Subatomic Particles in the Nucleus
In the nucleus of an atom, there are protons (p+) and neutrons (n0)
An unstable isotope that is subject to radioactive decay
Radioactive Decay
The breaking down of an unstable atomic nucleus to produce radiation and a more stable nucleus of a different element
Energy given off by the nucleus in the form of penetrating rays and particles
Nature of Radioactive Decay
Radioactive decay is spontaneous and does not require input of energy
The changing of 1 element into another element by radioactive decay
Factors of Nucleus Stability
The stability of a nucleus depends on ratio of neutrons to protons; too many or too few neutrons relative to protons makes it unstable
Elements with Greater Proclivities for Radioactivity
Elements with atomic number 84+ are considered to be radioactive; elements with odd mass numbers of protons and neutrons are also radioactive
Elements with Lower Proclivities for Radioactivity
Light elements where the ratio of n0 to p+ is 1 are considered to be stable; elements with even # p+ and n0 are considered more stable than their odd counterparts
An atom of an element with a different mass number
5 Radiation Types
Alpha Decay, Beta Decay, Gamma Radiation, Positron, Electron Capture
Alpha Decay
The first type of discovered decay; yields a Helium nucleus; is common for heavier elements; decreases mass # of daughter nuclide by 4, and its atomic # by 2; if need be, decreases neutrons, increases protons
Aspects of Alpha Particle
Neutral charge; only the helium nucleus is emitted; 4 mass #, +2 atomic #
Beta Decay
Increases atomic # of daughter nuclide by 1, while leaving mass # intact; produces and ejects an electron; produces a proton; if need be, increases neutrons, decreases protons
Aspects of Beta Particle
No mass #, -1 atomic #
Particle with an electron’s mass, but a proton’s charge; has no mass number, but +1 atomic #
Positron Decay
The decreasing of a parent isotope’s atomic #
Electron Capture
The capturing of an inner electron by the nucleus of its own atom; forms a nucleus; causes decrease of atomic #
Gamma Radiation
Allows nucleus to rid itself of excess energy for stabilization
Strong Nuclear Force
The force holding all nuclear particles close together; effective only at minuscule distances; opposes electrostatic forces that would normally separate particles of like charges
Band of Stability
The hypothetical line where the # of neutrons divided by the atomic # is 1; elements with atomic # of 20 and below are close to this line
Ratio of Neutrons to Protons
This ratio determines the radioactive decay that an element undergoes
The time it takes 1/2 of the nuclei of a radioactive substance to decay
Calculating Half-Life
N =N0 (1/2) n
where n = # ½ lives that have passed, No is initial amount, N = remaining amount (n= t/T, t =elapsed time, T= duration of half-life)
Ways Transmutation Can Occur
Transmutation can occur by either decay or bombardment
Hitting an atom with a particle to see what happens
Elements with atomic numbers above 92; all are man-made, radioactive; Np & Pu first artificial elements – produced in 1940s; since that time, over 20 artificial elements produced in particle accelerators or nuclear reactors
Decay Series
A series of radioisotopes produced by successive radioactive decay until a stable isotope is reached
Parent Nuclide
The heaviest radioisotope of each decay series
Daughter Nuclides
The radioisotopes produced by the decay of the parent nuclide
Radioactive Decay Rates
Radioactive decay rates are measured in half-lives; half-lives can range from nanoseconds to billions of years
Nuclear Fission
When the nucleus of a very heavy atom splits into more stable nuclei of smaller mass; the separation of atoms; releases nuclear energy; neutron collides with nucleus, splitting the nucleus and releasing nuclear energy; this process releases a great deal of energy (E=mc2), and is the basis for nuclear reactors and some atomic weapons
Nucleus Volume
Adding a neutron to a stable nucleus increases the volume of the nucleus; this decreases the nuclear strong force, increasing the activity of nuclear particles
Nuclear Fusion
Bonding of atoms; the process by which we get atoms; smaller atomic nuclei are joined, or fused, together to form a nucleus of greater mass; in general, fusion reactions release much larger quantities of energy than fission reactions
Fission Uses
Generating electricity, nuclear bombs
Iron and Fusion
Iron resists fusion; iron is the most stable element, meaning its nucleus releases the lowest amount of energy; as such, iron cannot be fused into heavier elements
Chain Reaction
This occurs when the material that starts the reaction is also one of the products of the reaction and can start another reaction with fissionable material
Critical Mass
A sample of fissionable material must have sufficient mass to in order for a chain reaction to occur and be sustained
Neutron Moderation
Slowing down the n so that they are captured by the material in order to continue the reaction – if the n are moving too fast, they will pass through the nucleus and not be absorbed, water or carbon are used as moderators
Neutron Absorption
Trapping the slower-moving n before they hit fissionable material – requires control rods, often made of Cd
Conversion Reaction In a Star
The net conversion of hydrogen nuclei to helium nuclei releases so much energy because energy in a star is released with a velocity equal to the square of the speed of light
Formation of Elements from Supernovas
When supernova detonation, the explosion of a supernova, commences, the dense core, which following the collapse of the star became solely comprised of neutrons, reflects the outer layers of the star that fall unto the core; the resulting shock waves are so grand that they force nuclear particles to bond, creating heavy elements
Categories: Nuclear Chemistry