Guys, does anyone know the answer?
get after a radioactive atom decays, it is the same element that it was before with no measurable change in mass. which kind of decay has occurred, and how do you know? alpha decay because alpha particles have no mass beta decay because this kind of decay cannot change one element into another alpha decay because it creates a new isotope of the same element gamma decay because photons have no mass from EN Bilgi.
Radioactive decay types article (article)
Radioactive decay types article
What are nuclear reactions?
Sometimes atoms aren’t happy just being themselves; they suddenly change into completely different atoms, without any warning. This mysterious transformation of one type of element into another is the basis of nuclear reactions, which cause one nucleus to change into a different nucleus. Just like chemical reactions cause compounds to turn into other compounds by swapping their electrons, nuclear reactions happen when the number of protons and neutrons in the nucleus of an atom change.
Some types of nuclear reactions can actually kick protons out of the nucleus, or convert them into neutrons. Since we know what to call an element by looking up its number on a periodic table and then reading off its name, when the atomic number (number of protons) changes, so does the name of the element. This makes nuclear reactions look somewhat like alchemy: an atom of potassium (atomic number 19) can suddenly and unexpectedly transform into an atom calcium (atomic number 20). The only sign that anything has changed is the release of radiation, which we’ll talk more about in a little bit.
Even more strangely, nuclear reactions often occur almost entirely randomly. If you have a single nucleus that you are certain will eventually decay into a different nucleus, you still have only a rough idea how long it will take for you to see it happen. You could be sitting watching the nucleus for anywhere between a few seconds to your entire lifetime, and at some point it would suddenly decay without any warning! However, depending on the type of nucleus, you can predict how long on average it would take to decay if you watched many nuclei at once. So while the average time to decay is a measurable number (for potassium it’s over a billion years), the exact time of the decay is entirely random.
There are three types of nuclear reaction, each of which cause the nucleus to shoot out a different, fast-moving particle (like a photon or electron). These released particles are a side effect of the element changing its atomic number or mass, and they are what scientists generally mean when they warn about nuclear radiation, since fast-moving particles can act like tiny bullets that poke holes in your body. However, much nuclear radiation is actually harmless, and it occasionally can be harnessed to provide new type of medical or diagnostic tools.
Why do nuclear reactions happen?
Not all elements undergo nuclear decay over timescales that we can observe. Some elements take millions of years to decay. In fact, most living things primarily consist of isotopes of carbon and nitrogen, which have such incredibly long lifetimes that they will essentially never decay within the lifespan of the organism. This is necessary because the biochemical function of each of these atoms is specifically tied to its atomic number: if a nervous receptor specifically seeks out and binds a carbon-based signalling molecule, then it won’t work if that carbon spontaneously changes into beryllium.
Different atoms of the same element can have different masses. For example, an atom of carbon (atomic number 6, so six protons) can have either 6 neutrons or 8 neutrons. The former case is more familiar from chemistry class, since a lot of the common light elements used in biology (like oxygen, carbon, and nitrogen) have the same number of protons as neutrons. But it turns out that the case of carbon having 6 protons and 8 neutrons, while not as stable as 6 and 6, is stable enough that it can actually occur in nature in observable amounts. Because the 8 neutron nucleus and the 6 neutron nucleus are technically both carbon, we call them different isotopes of carbon.
Since protons and neutrons have roughly the same mass, the more common version of carbon is called carbon-12 (6 protons + 6 neutrons). The heavier isotope is called carbon-14 (6 protons + 8 neutrons). But when you look up the mass of carbon on the periodic table, it says that the mass is 12.011 atomic mass units (amu). This is because if you went out and weighed a huge batch of carbon atoms, most of the atoms you would find would weigh exactly 12 amu. But within that huge batch you’d occasionally find a carbon-14 nucleus, which would skew the average of your measurements to a value slightly higher than 12.
For reasons that are deeply related to the fundamental forces that act in the nucleus, the tendency of a substance to undergo nuclear decay is related to both the atomic number and the atomic mass of an element. This means that two different isotopes of the same element will have different tendencies to undergo nuclear decay. In the case of carbon, the isotope carbon-14 wants to decay into nitrogen while carbon-12 (which is most of the carbon in your body) would remain stable.
As a result, knowing which isotope is present in a sample of element not only tells us the sample’s stability, but also the type of decay it will undergo.
What are the types of nuclear reaction?
Cartoon showing alpha decay.
During alpha decay, a nucleus actually breaks up into two chunks: a pair of protons bound to a pair of neutrons (a collection of four particles which is essentially a helium nucleus, and is called an alpha particle), and another piece constituting the original nucleus minus this chunk. So we can actually write down a chemical reaction equation for alpha decay:
Radioactive Decay Related terms:
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Unstable Nuclei and Radioactive Decay
GREGORY R. CHOPPIN, ... JAN RYDBERG, in Radiochemistry and Nuclear Chemistry (Third Edition), 2002
4.1 Radioactive decay
Radioactive decay is a spontaneous nuclear transformation that has been shown to be unaffected by pressure, temperature, chemical form, etc (except a few very special cases). This insensitivity to extranuclear conditions allows us to characterize radioactive nuclei by their decay period and their mode and energy of decay without regard to their physical or chemical condition.
The time dependence of radioactive decay is expressed in terms of the half-life (t½), which is the time required for one-half of the radioactive atoms in a sample to undergo decay. In practice this is the time for the measured radioactive intensity (or simply, radioactivity of a sample) to decrease to one-half of its previous value (see Fig. 1.1). Half-lives vary from millions of years to fractions of seconds. While half-lives between a minute and a year are easily determined with fairly simple laboratory techniques, the determination of much shorter half-lives requires elaborate techniques with advanced instrumentation. The shortest half-life measurable today is about 10−18 s. Consequently, radioactive decay which occurs with a time period less than 10−18 s is considered to be instantaneous. At the other extreme, if the half-life of the radioactive decay exceeds 1015 y, the decay usually cannot be observed above the normal signal background present in the detectors. Therefore, nuclides which may have half-lives greater than 1015 y are normally considered to be stable to radioactive decay. However, a few unstable nuclides with extremely long half-lives, ≥ 1020 y, have been identified. It should be realized that 1015 y is about 105 times larger than the age of the universe.
Radioactive decay involves a transition from a definite quantum state of the original nuclide to a definite quantum state of the product nuclide. The energy difference between the two quantum levels involved in the transition corresponds to the decay energy. This decay energy appears in the form of electromagnetic radiation and as the kinetic energy of the products, see Element and Nuclide Index for decay energies.
The mode of radioactive decay is dependent upon the particular nuclide involved. We have seen in Ch. 1 that radioactive decay can be characterized by α-, β-, and γ-radiation. Alpha-decay is the emission of helium nuclei. Beta-decay is the creation and emission of either electrons or positrons, or the process of electron capture. Gamma-decay is the emission of electromagnetic radiation where the transition occurs between energy levels of the same nucleus. An additional mode of radioactive decay is that of internal conversion in which a nucleus loses its energy by interaction of the nuclear field with that of the orbital electrons, causing ionization of an electron instead of γ-ray emission. A mode of radioactive decay which is observed only in the heaviest nuclei is that of spontaneous fission in which the nucleus dissociates spontaneously into two roughly equal parts. This fission is accompanied by the emission of electromagnetic radiation and of neutrons. In the last decade also some unusual decay modes have been observed for nuclides very far from the stability line, namely neutron emission and proton emission. A few very rare decay modes like 12C-emission have also been observed.
In the following, for convenience, we sometimes use an abbreviated form for decay reactions, as illustrated for the 238U decay chain in §1.3:
or, if half-lives are of importance:
238U(α,4.5×109y)234Th(β−,24 d)234Pa(β−,1.1min)234U(α,2.5×105y), etc.
In the following chapter we discuss the energetics of the decay processes based on nuclear binding energy considerations and simple mechanics, then we consider the kinetics of the processes. In Ch. 11, where the internal properties of the nuclei are studied, the explanations of many of the phenomena discussed in this chapter are presented in terms of simple quantum mechanical rules.
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AIR–SEA INTERACTION | Gas Exchange
P.D. Nightingale, in Encyclopedia of Atmospheric Sciences, 2003
Radioactive decay of radium-226 (226Ra) to the gas radon-222 (222Rn) occurs within the water column and radon is therefore transferred from the surface mixed layer to the atmosphere. A mass budget can be made of the ‘missing’ radon by assuming steady state with deeper waters and a value for kRn can be derived. The mean value for kCO2 obtained using this technique is about 14 cm h−1 (corrected from kRn by assuming n0.5). The radon data show a large amount of scatter with wind speed and the technique has shortcomings in that the condition of steady state is rarely fulfilled.
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Peter Airey, ... John Twining, in Radioactivity in the Environment, 2012
18.104.22.168 Precision of Radioactivity Measurements
Radioactive decay is a random process. Although the rate of decay for a specific radionuclide can be calculated from knowledge of the number of radioactive atoms and the half-life, there is no way of knowing which specific radioactive atom will decay in which time interval. Furthermore, in all practical circumstances, the probability of a given radioactive atom decaying in a particular time interval is extremely small.3This situation is best described by the Poisson statistics.
17.3: Types of Radioactivity
The major types of radioactivity include alpha particles, beta particles, and gamma rays. Fission is a type of radioactivity in which large nuclei spontaneously break apart into smaller nuclei.
17.3: Types of Radioactivity- Alpha, Beta, and Gamma Decay
Last updated Feb 26, 2021
17.2: The Discovery of Radioactivity
17.4: Detecting Radioactivity
Compare qualitatively the ionizing and penetration power of alpha particles
(α) (α) , beta particles (β) (β) , and gamma rays (γ) (γ) .
Express the changes in the atomic number and mass number of a radioactive nuclei when an alpha, beta, or gamma particle is emitted.
Write nuclear equations for alpha and beta decay reactions.
Many nuclei are radioactive; that is, they decompose by emitting particles and in doing so, become a different nucleus. In our studies up to this point, atoms of one element were unable to change into different elements. That is because in all other types of changes discussed, only the electrons were changing. In these changes, the nucleus, which contains the protons that dictate which element an atom is, is changing. All nuclei with 84 or more protons are radioactive, and elements with less than 84 protons have both stable and unstable isotopes. All of these elements can go through nuclear changes and turn into different elements.
In natural radioactive decay, three common emissions occur. When these emissions were originally observed, scientists were unable to identify them as some already known particles and so named them:
alpha particles ( α α ) beta particles (β) (β) gamma rays (γ) (γ)
These particles were named using the first three letters of the Greek alphabet. Some later time, alpha particles were identified as helium-4 nuclei, beta particles were identified as electrons, and gamma rays as a form of electromagnetic radiation like x-rays, except much higher in energy and even more dangerous to living systems.
The Ionizing and Penetration Power of Radiation
With all the radiation from natural and man-made sources, we should quite reasonably be concerned about how all the radiation might affect our health. The damage to living systems is done by radioactive emissions when the particles or rays strike tissue, cells, or molecules and alter them. These interactions can alter molecular structure and function; cells no longer carry out their proper function and molecules, such as DNA, no longer carry the appropriate information. Large amounts of radiation are very dangerous, even deadly. In most cases, radiation will damage a single (or very small number) of cells by breaking the cell wall or otherwise preventing a cell from reproducing.
The ability of radiation to damage molecules is analyzed in terms of what is called ionizing power. When a radiation particle interacts with atoms, the interaction can cause the atom to lose electrons and thus become ionized. The greater the likelihood that damage will occur by an interaction is the ionizing power of the radiation.
Much of the threat from radiation is involved with the ease or difficulty of protecting oneself from the particles. How thick of a wall do you need to hide behind to be safe? The ability of each type of radiation to pass through matter is expressed in terms of penetration power. The more material the radiation can pass through, the greater the penetration power and the more dangerous it is. In general, the greater mass present, the greater the ionizing power, and the lower the penetration power.
Comparing only the three common types of ionizing radiation, alpha particles have the greatest mass. Alpha particles have approximately four times the mass of a proton or neutron and approximately 8,000 times the mass of a beta particle. Because of the large mass of the alpha particle, it has the highest ionizing power and the greatest ability to damage tissue. That same large size of alpha particles, however, makes them less able to penetrate matter. They collide with molecules very quickly when striking matter, add two electrons, and become a harmless helium atom. Alpha particles have the least penetration power and can be stopped by a thick sheet of paper or even a layer of clothes. They are also stopped by the outer layer of dead skin on people. This may seem to remove the threat from alpha particles, but it is only from external sources. In a nuclear explosion or some sort of nuclear accident, where radioactive emitters are spread around in the environment, the emitters can be inhaled or taken in with food or water and once the alpha emitter is inside you, you have no protection at all.
Beta particles are much smaller than alpha particles and therefore, have much less ionizing power (less ability to damage tissue), but their small size gives them much greater penetration power. Most resources say that beta particles can be stopped by a one-quarter inch thick sheet of aluminum. Once again, however, the greatest danger occurs when the beta emitting source gets inside of you.
Gamma rays are not particles, but a high energy form of electromagnetic radiation (like x-rays, except more powerful). Gamma rays are energy that has no mass or charge. Gamma rays have tremendous penetration power and require several inches of dense material (like lead) to shield them. Gamma rays may pass all the way through a human body without striking anything. They are considered to have the least ionizing power and the greatest penetration power.