The physics governing activity within atomic nuclei.
The structure of the atom
At the heart of nuclear physics is the structure of atoms. Atoms are composed of three subatomic particles: protons, neutrons and electrons. Protons have a positive charge, while neutrons have no charge at all. Electrons carry a negative charge and orbit around the nucleus, made up of protons and neutrons, in shells or energy levels. The number of protons in an atom determines its atomic number, which identifies it as a particular element on the periodic table. Different numbers of neutrons in nuclei results in different forms of the same element. The protons and electrons in an atom give it its charge. The total number of protons and neutrons in an atomic nucleus give the atom its mass.
The arrangement within an atom is determined by quantum mechanics; each electron occupies one orbital shell with specific energy levels depending on their distance from the nucleus. This arrangement allows for chemical reactions between atoms since they can share electrons between them when forming bonds with other elements – this process is known as covalent bonding.
The nuclear force
The nuclear force is the strong attractive force that binds protons and neutrons – known as nucleons – together in an atomic nucleus. It has an almost identical effect on both neutrons and protons. It was first proposed by Hideki Yukawa in 1935, who called it the meson theory of nuclear forces. This force acts over a very short distance, typically less than one femtometer (10^-15 m). It is repulsive at distances of less than 0.7 femtometers, but is most strongly attractive at 0.8 femtometers. Beyond this, it rapidly dwindles to negligible effects around 2.5 femtometers.
As the strength of the nuclear force diminishes, the repulsive electromagnetic force between protons begins to dominate and causes nuclei to become unstable. However, at shorter distances, the attractive nuclear force becomes stronger and holds nuclei together despite their positive charges. This balance between attraction and repulsion is what gives atoms their structure. The nuclear force has a vital role in storing the energy which is used in creating nuclear power or detonating nuclear weapons.
The binding energy of nuclei
Nuclear binding energy is the energy required to form a nucleus from its constituent protons and neutrons, or break it apart. It is related to the mass defect between the expected and observed nuclear mass; when nuclei are formed, some of their mass is converted into energy according to Einstein’s famous equation E=mc2. Heavier elements tend to have more binding energy than lighter ones – for example, uranium has about 7 million electron volts (MeV) of binding energy per atom compared to just 4 MeV for one form of helium!
The amount of binding energy released during a nuclear reaction can be enormous. In fact, one gram of plutonium or uranium can release around 1 MW of power a day through nuclear fission- about the same as burning 3 tons of coal in a day. This explains why fission reactions are so powerful and why fusion reactions could potentially provide an almost limitless source of clean renewable energy. In addition, understanding how much binding energy different elements possess helps us understand why certain isotopes are stable while others decay quickly over time.
Radioactivity
Radioactivity is the process by which unstable nuclei emit radiation or particles in order to become more stable. This occurs when a nucleus has an imbalance of protons and neutrons, resulting in an excess of energy that must be released for it to reach equilibrium.
For example, uranium-235 is unstable due to excessive repulsive forces between protons in its nucleus. It emits alpha particles – consisting of 2 neutrons and 2 protons – with the resulting product of thorium-231. These atoms in themselves are unstable, and continue to undergo radioactive decay, with the eventual product of the stable lead-207.
The rate at which radioactive decay occurs can vary greatly depending on the element involved; some elements such as uranium-238 have half lives measured in thousands or millions of years while others like technetium-99m have half lives measured in days or even hours! The half life of an element is the time it takes for half the sample to decay through radioactivity.
Explain the terms Alpha, beta, and gamma decay
Alpha, beta and gamma decay are all forms of radioactive decay. Alpha particles consist of two protons and two neutrons, while beta particles are electrons or positrons emitted from the nucleus. Gamma decay involves a loss of energy by the nucleus. Gamma radiation is highly energetic and can penetrate matter more deeply than alpha or beta radiation.
Alpha and beta decays differ from gamma decay in that they involve a change in the number of protons or neutrons within an atom’s nucleus; this is known as transmutation. In alpha decay, a heavy element such as uranium will emit an alpha particle to become a lighter element like thorium. Similarly, in beta decay, a neutron is turned into a proton when an electron is emitted by the nucleus, or a proton is turned into a neutron when a positron is emitted. This changes the nature of the atom by altering its atomic number (the number of protons) and mass number (the total number of nucleons – protons plus neutrons).
In contrast, gamma radiation does not cause any transmutation since it only involves energy being released without changing the composition of the atom itself.
Nuclear reactions
Nuclear reactions are processes that involve changes in the nucleus of an atom. These include nuclear fusion or nuclear fission, both of which release large amounts of energy.
In nuclear fusion, two light nuclei combine to form a heavier one, releasing energy in the process. This is what powers stars like our sun and is responsible for creating elements heavier than iron. Nuclear fission involves splitting a heavy nucleus into two lighter ones, also releasing energy in the process. This type of reaction has been harnessed to generate electricity on Earth through power plants such as those found at Chernobyl and Fukushima Daiichi.
The amount of energy released by these reactions is immense; it takes just 1 gram (0.035 ounces) of uranium-235 to produce as much energy as burning 3 tons (3000 kilograms) of coal! The potential applications for this technology are vast but must be used responsibly due to its destructive capabilities if not handled correctly. Historically, it hasn’t been possible for humans to produce energy using nuclear fusion, but scientific advances have changed that. In December 2022, scientists were able to produce an energy gain using nuclear fusion – opening up exciting possibilities for the future.
Artificial transmutation
Artificial transmutation is the process of transforming one element into another through nuclear reactions. It involves manipulating the nucleus of an atom to change its number of protons and neutrons. This can be done by bombarding it with fundamental particles such as alpha particles or protons.
The fundamental particles used in artificial transmutation include protons and neutrons. Protons have a positive charge while neutrons have no charge; both are found in the nucleus of atoms. By changing the number of these subatomic particles within an atom’s nucleus, different elements can be created from existing ones.
One example of artificial transmutation is nitrogen-14 being transformed into oxygen-17 through bombardment with alpha particles (helium nuclei). In this reaction two protons and two neutrons are added to nitrogen-14’s seven protons and seven neutrons to create oxygen-17 which has eight protons and nine neutrons plus an atom of hydrogen. Thus the atom’s atomic number is changed from 7 to 8!
Artificial transmutation has also been used for medical purposes such as creating radioactive isotopes for use in cancer treatments or imaging scans like PET scans (positron emission tomography).
Nuclear reactors
Nuclear reactors are used to generate electricity by harnessing the energy released from nuclear fission reactions. In a typical reactor, uranium fuel rods are placed in a core and bombarded with neutrons which cause the uranium atoms to split into smaller atoms, releasing heat energy. This heat is then used to boil water which produces steam that drives turbines connected to generators, producing electricity.
The main benefit of nuclear power is its efficiency; one kilogram of uranium can produce as much energy as burning 2.7 million kilograms of coal! Nuclear reactors also have low emissions compared to other sources of energy such as fossil fuels and do not contribute significantly to global warming or air pollution. Additionally, they require less land than other forms of power generation such as wind turbines.
However, there are some drawbacks associated with nuclear power plants including safety concerns due to potential radiation leaks and long-term storage issues for radioactive waste products produced during operation. Furthermore, building new reactors requires large investments in infrastructure and technology which can be expensive and time consuming. Despite these drawbacks though, many countries around the world continue to use nuclear power for their electricity needs.
