The electric force may be weaker than the strong nuclear force, but the strong force has a much more limited range: in an iron nucleus, each proton repels the other 25 protons, while the nuclear force only binds close neighbors. So for larger nuclei, the electrostatic forces tend to dominate and the nucleus will tend over time to break up. As nuclei grow bigger still, this disruptive effect becomes steadily more significant. By the time polonium is reached 84 protonsnuclei can no longer accommodate their large positive charge, but emit their excess protons quite rapidly in the process of alpha radioactivity-the emission of helium nuclei, each containing two protons and two neutrons.
Helium nuclei are an especially stable combination.
Because of this process, nuclei with more than 94 protons are not found naturally on Earth see periodic table. The isotopes beyond uranium atomic number 92 with the longest half-lives are plutonium 80 million years and curium 16 million years. The nuclear fusion process works as follows: five billion years ago, the new Sun formed when gravity pulled together a vast cloud of hydrogen and dust, from which the Earth and other planets also arose.
The gravitational pull released energy and heated the early Sun, much in the way Helmholtz proposed. Thermal energy appears as the motion of atoms and molecules: the higher the temperature of a collection of particles, the greater is their velocity and the more violent are their collisions. When the temperature at the center of the newly formed Sun became great enough for collisions between hydrogen nuclei to overcome their electric repulsion, and bring them into the short range of the attractive nuclear forcenuclei began to stick together.
When this began to happen, protons combined into deuterium and then helium, with some protons changing in the process to neutrons plus positrons, positive electrons, which combine with electrons and annihilate into gamma-ray photons. This released nuclear energy now keeps up the high temperature of the Sun's core, and the heat also keeps the gas pressure high, keeping the Sun at its present size, and stopping gravity from compressing it any more.
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There is now a stable balance between gravity and pressure. Different nuclear reactions may predominate at different stages of the Sun's existence, including the proton-proton reaction and the carbon-nitrogen cycle-which involves heavier nuclei, but whose final product is still the combination of protons to form helium. A branch of physics, the study of controlled nuclear fusionhas tried since the s to derive useful power from nuclear fusion reactions that combine small nuclei into bigger ones, typically to heat boilers, whose steam could turn turbines and produce electricity.
Unfortunately, no earthly laboratory can match one feature of the solar powerhouse: the great mass of the Sun, whose weight keeps the hot plasma compressed and confines the nuclear furnace to the Sun's core.
Instead, physicists use strong magnetic fields to confine the plasma, and for fuel they use heavy forms of hydrogen, which burn more easily. Magnetic traps can be rather unstable, and any plasma hot enough and dense enough to undergo nuclear fusion tends to slip out of them after a short time.
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Even with ingenious tricks, the confinement in most cases lasts only a small fraction of a second. Exciton binding energy has been predicted to be key for efficient solar cells due to recent studies.
Small nuclei that are larger than hydrogen can combine into bigger ones and release energy, but in combining such nuclei, the amount of energy released is much smaller compared to hydrogen fusion.
The reason is that while the overall process releases energy from letting the nuclear attraction do its work, energy must first be injected to force together positively charged protons, which also repel each other with their electric charge. For elements that weigh more than iron a nucleus with 26 protonsthe fusion process no longer releases energy.
In even heavier nuclei energy is consumed, not released, by combining similarly sized nuclei. With such large nuclei, overcoming the electric repulsion which affects all protons in the nucleus requires more energy than is released by the nuclear attraction which is effective mainly between close neighbors.
Conversely, energy could actually be released by breaking apart nuclei heavier than iron. With the nuclei of elements heavier than leadthe electric repulsion is so strong that some of them spontaneously eject positive fragments, usually nuclei of helium that form very stable combinations alpha particles.
This spontaneous break-up is one of the forms of radioactivity exhibited by some nuclei.
Nuclei heavier than lead except for bismuththoriumand uranium spontaneously break up too quickly to appear in nature as primordial elementsthough they can be produced artificially or as intermediates in the decay chains of heavier elements. Generally, the heavier the nuclei are, the faster they spontaneously decay. Iron nuclei are the most stable nuclei in particular ironand the best sources of energy are therefore nuclei whose weights are as far removed from iron as possible.
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One can combine the lightest ones-nuclei of hydrogen protons -to form nuclei of helium, and that is how the Sun generates its energy. Alternatively, one can break up the heaviest ones-nuclei of uranium or plutonium-into smaller fragments, and that is what nuclear reactors do.
An example that illustrates nuclear binding energy is the nucleus of 12 C carbonwhich contains 6 protons and 6 neutrons. The protons are all positively charged and repel each other, but the nuclear force overcomes the repulsion and causes them to stick together.
The nuclear force is a close-range force it is strongly attractive at a distance of 1. The nuclear force also pulls neutrons together, or neutrons and protons. The energy of the nucleus is negative with regard to the energy of the particles pulled apart to infinite distance just like the gravitational energy of planets of the solar systembecause energy must be utilized to split a nucleus into its individual protons and neutrons.
The binding energy of helium is the energy source of the Sun and of most stars. The sun is composed of 74 percent hydrogen measured by massan element having a nucleus consisting of a single proton. Energy is released in the sun when 4 protons combine into a helium nucleus, a process in which two of them are also converted to neutrons. The conversion of protons to neutrons is the result of another nuclear force, known as the weak nuclear force.
The weak force, like the strong force, has a short range, but is much weaker than the strong force. The weak force tries to make the number of neutrons and protons into the most energetically stable configuration. For nuclei containing less than 40 particles, these numbers are usually about equal.
Protons and neutrons are closely related and are collectively known as nucleons. As the number of particles increases toward a maximum of aboutthe number of neutrons to maintain stability begins to outstrip the number of protons, until the ratio of neutrons to protons is about three to two.
The protons of hydrogen combine to helium only if they have enough velocity to overcome each other's mutual repulsion sufficiently to get within range of the strong nuclear attraction.
This means that fusion only occurs within a very hot gas. Hydrogen hot enough for combining to helium requires an enormous pressure to keep it confined, but suitable conditions exist in the central regions of the Sun, where such pressure is provided by the enormous weight of the layers above the core, pressed inwards by the Sun's strong gravity.
The process of combining protons to form helium is an example of nuclear fusion. The earth's oceans contain a large amount of hydrogen that could theoretically be used for fusion, and helium byproduct of fusion does not harm the environment, so some consider nuclear fusion a good alternative to supply humanity's energy needs. Experiments to generate electricity from fusion have so far only partially succeeded. Sufficiently hot hydrogen must be ionized and confined.
One technique is to use very strong magnetic fields, because charged particles like those trapped in the Earth's radiation belt are guided by magnetic field lines. Fusion experiments also rely on heavy hydrogenwhich fuses more easily, and gas densities can be moderate. But even with these techniques far more net energy is consumed by the fusion experiments than is yielded by the process. In the main isotopes of light nuclei, such as carbon, nitrogen and oxygen, the most stable combination of neutrons and of protons are when the numbers are equal this continues to element 20, calcium.
However, in heavier nuclei, the disruptive energy of protons increases, since they are confined to a tiny volume and repel each other. The energy of the strong force holding the nucleus together also increases, but at a slower rate, as if inside the nucleus, only nucleons close to each other are tightly bound, not ones more widely separated.
The net binding energy of a nucleus is that of the nuclear attraction, minus the disruptive energy of the electric force. As nuclei get heavier than helium, their net binding energy per nucleon deduced from the difference in mass between the nucleus and the sum of masses of component nucleons grows more and more slowly, reaching its peak at iron. As nucleons are added, the total nuclear binding energy always increases-but the total disruptive energy of electric forces positive protons repelling other protons also increases, and past iron, the second increase outweighs the first.
Iron 56 Fe is the most efficiently bound nucleus  meaning that it has the least average mass per nucleon. However, nickel is the most tightly bound nucleus in terms of energy of binding per nucleon. To reduce the disruptive energy, the weak interaction allows the number of neutrons to exceed that of protons-for instance, the main isotope of iron has 26 protons and 30 neutrons. Isotopes also exist where the number of neutrons differs from the most stable number for that number of nucleons.
If the ratio of protons to neutrons is too far from stability, nucleons may spontaneously change from proton to neutron, or neutron to proton. The two methods for this conversion are mediated by the weak force, and involve types of beta decay. In the simplest beta decay, neutrons are converted to protons by emitting a negative electron and an antineutrino. This is always possible outside a nucleus because neutrons are more massive than protons by an equivalent of about 2.
In the opposite process, which only happens within a nucleus, and not to free particles, a proton may become a neutron by ejecting a positron. This is permitted if enough energy is available between parent and daughter nuclides to do this the required energy difference is equal to 1.
If the mass difference between parent and daughter is less than this, a proton-rich nucleus may still convert protons to neutrons by the process of electron capturein which a proton simply electron captures one of the atom's K orbital electrons, emits a neutrino, and becomes a neutron. Among the heaviest nuclei, starting with tellurium nuclei element 52 containing or more nucleons, electric forces may be so destabilizing that entire chunks of the nucleus may be ejected, usually as alpha particleswhich consist of two protons and two neutrons alpha particles are fast helium nuclei.
Beryllium-8 also decays, very quickly, into two alpha particles.
UNC: Valuable Minerals. To maintain its fleets and continue to expand, the Alliance must find new resources wherever it can. You've recently surveyed an important deposit and claimed it for the Alliance. There must be more like them in the Traverse. Jun 06, After Shepard's Choice (naturalhealthnwellness.comfect) submitted 1 month ago by TheGrizzlyBaron. So, after Commander Shepard's choice at the end of Mass Effect 3 all of the relays are destroyed in order to carry the destroy/control/evolve signal. The plutonium isotope Pu is an alpha emitter with a half life of 87 years. These characteristics make it well suited for electrical power generation for devices which must function without direct maintenance for timescales approximating a human life time.
Alpha particles are extremely stable. This type of decay becomes more and more probable as elements rise in atomic weight past The curve of binding energy is a graph that plots the binding energy per nucleon against atomic mass.
This curve has its main peak at iron and nickel and then slowly decreases again, and also a narrow isolated peak at helium, which as noted is very stable.
The heaviest nuclei in nature, uranium U, are unstable, but having a half-life of 4.
The most common isotope of thorium, Th, also undergoes alpha particle emission, and its half-life time over which half a number of atoms decays is even longer, by several times. In each of these, radioactive decay produces daughter isotopes that are also unstable, starting a chain of decays that ends in some stable isotope of lead.
Asked 8 years, 9 months ago. Active 7 years, 8 months ago.
Viewed 21k times. I decided to get in to Mass Effect, since the series seems rather good. Jupotter 7, 7 7 gold badges 42 42 silver badges 76 76 bronze badges.
KdgDev KdgDev 3 3 gold badges 5 5 silver badges 9 9 bronze badges. You really need to get the name of the planet.
Some of the interactable objects are quest-related if I remember correctlyand the only way to tell if that's the case in your case is by getting the name of the planet. Still, there's no pop-up that indicated I could actually get out of the vehicle and nothing in the control configuration.
Would that mean I'm not meant to get out or am I just missing something? As Fabian mentions, you need to exit the vehicle to interact with these objects. Raven Dreamer Raven Dreamer k gold badges silver badges bronze badges. They really should've said this in their tooltip instructions.
Thank god for google. Mad Scientist Mad Scientist The metal has a silvery appearance and takes on a yellow tarnish when slightly oxidized. It is chemically reactive. A relatively large piece of plutonium is warm to the touch because of the energy given off in alpha decay. Larger pieces will produce enough heat to boil water.
The metal readily dissolves in concentrated hydrochloric acid, hydroiodic acid, or perchloric acid.
The metal exhibits six allotropic modifications having various crystalline structures. The densities of these vary from The most important isotope of plutonium is Pu, with a half-life of 24, years. Because of its short half-life, there are only extremely tiny trace amounts of plutonium naturally in uranium ores.
The mass defect of a nucleus represents the amount of mass equivalent to the binding energy of the nucleus (E=mc 2), which is the difference between the mass of a nucleus and the sum of the individual masses of the nucleons of which it is composed. Can I pick up items in Mass Effect while in a vehicle? Ask Question Asked 8 years, 9 months ago. Active 7 years, 8 months ago. Viewed 21k times 8. I decided to get in to Mass Effect, since the series seems rather good. Currently, I'm on a side-quest, riding a vehicle on . Apr 21, Mass Effect: Andromeda's eponymous galaxy is full of minerals (and tech and biology materials). You'll use all of these to craft weapons, armor and upgrades for yourself and your naturalhealthnwellness.com: Jeffrey Parkin.
Fifteen isotopes of plutonium are known. Applications Plutonium is a key fissile component in modern nuclear weapons ; care must be taken to avoid accumulation of amounts of plutonium which approach critical massthe amount of plutonium which will self-generate a nuclear reaction. Despite not being confined by external pressure as is required for a nuclear weapon, it will nevertheless heat itself and break whatever confining environment it is in.
Shape is relevant; compact shapes such as spheres are to be avoided. Plutonium could also be used to manufacture radiological weapons. The plutonium isotope Pu is an alpha emitter with a half life of 87 years. These characteristics make it well suited for electrical power generation for devices which must function without direct maintenance for timescales approximating a human life time.
Plutonium was used on the Apollo lunar flight in to power seismic devices and other equipment left on the Moon, and it was also the power supply of the two Voyager supercraft launched in Plutonium can also be used as a fuel in a new generation of fast-breeder nuclear weapons, which burn a mixed oxide MOX fuel consisting of uranium and plutonium.
Trace amounts of plutonium are found naturally in uranium-rich ores.