What makes a substance radioactive?
Topic: What is a research question in science fair
May 26, 2019 / By Florry Question:
I'm doing a science fair project in which i will be testing the radioactivity of common household objects. unfortunately, i have to have at least 2 pages of background information. this is one of the questions i should answer in my background info.
Best Answers: What makes a substance radioactive?
Damiana | 8 days ago
Bob's answer is wonderfully detailed and is a good explanation, but I suspect might be too technical for your level. You may also find that sources like wikipedia are a little technical as well. I'd suggest you start by considering the three major modes of decay - alpha, beta, and gamma. A nice illustration can be found here: http://library.thinkquest.org/3471/radia... and other relevant material is here: http://en.wikipedia.org/wiki/Radioactive... - just that section.
As for how we know which decay will occur, we often look at the neutron-to-proton ratio. There is a "zone of stability", shown here: http://library.tedankara.k12.tr/chemistr... within which nuclei are stable (non-radioactive). Nuclei outside the zone are radioactive. The zone terminates at lead (Z = 82)... all nuclei beyond that are radioactive. Large nuclei typically are too large to be stable (too many protons) and typically undergo alpha decay. Nuclei with two many neutrons for the number of protons typically undergo beta-decay (in which a neutron decays into a proton, which remains in the nucleus, and an electron which is ejected as a beta particle). The zone of stability diagram also shows positron decay, which can happen if there are too many protons for the number of neutrons.
Wikipedia shows a bunch of other decay processes, but alpha, beta, and gamma decay and positron emission are the most common. Gamma decay often accompanies alpha or beta - cobalt-60, for example, undergoes beta, gamma decay emitting both a beta particle and a gamma ray.
If you want to see how many stable and unstable (radioactive) isotopes an element has, have a look at webelements. You might look particularly at technetium, which is unusual in that it is not that heavy but has no stable isotope. Webelements will also give you information on half-lives, which is the time taken for half of a sample to decay.
OK, I think that should be enough to get you started on your research. :)
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Originally Answered: What happens to the rate of radioactive decay as the mass of radioactive material decreases?
"3.Why is each toss in this simulation called a half life?"
The probability for a coin showing head up or tail up is p=1/2. In the first trial one expects 50% of 50 pennies= 25 pennies to be decayed. Next, with 25 pennies, 12.5 pennies should have been decayed. In the third run 6.25 pennies are expected to have been decayed.. The key number of this simulation is 2 and because the number of pennies are halved by each run the "time" elapsed is a half life.
"4. What is happening to the simulated rate of decay as the number of pennies decreases?"
rate= -ΔN/Δt = (N₀-N) /Δt.. Now let Δt be the time of a run= constant. and set it 1 sec for convenience.
and so on. You see the rate is decreasing
"5.What happens to the rate of radioactive decay as the mass of radioactive material decreases?"
Since mass is proportional to mole ( 1/M) results from question 4 can be taken in to consideration: rate decreases until it becomes zero because no radioactive material is left over.
"6.In what way does the data gathered during this investigation simulate the nature of half life?"
In a stochastic process.
The neutrons and protons that constitute nuclei, as well as other particles that may approach them, are governed by several interactions. The strong nuclear force, not observed at the familiar macroscopic scale, is the most powerful force over subatomic distances. The electrostatic force is also significant, while the weak nuclear force is responsible for beta decay.
The interplay of these forces is simple. Some configurations of the particles in a nucleus have the property that, should they shift ever so slightly, the particles could fall into a lower-energy arrangement (with the extra energy moving elsewhere). One might draw an analogy with a snowfield on a mountain: while friction between the snow crystals can support the snow's weight, the system is inherently unstable with regard to a lower-potential-energy state, and a disturbance may facilitate the path to a greater entropy state (i.e., towards the ground state where heat will be produced, and thus total energy is distributed over a larger number of quantum states). Thus, an avalanche results. The total energy does not change in this process, but because of entropy effects, avalanches only happen in one direction, and the end of this direction, which is dictated by the largest number of chance-mediated ways to distribute available energy, is what we commonly refer to as the "ground state".
Such a collapse (a decay event) requires a specific activation energy. In the case of a snow avalanche, this energy classically comes as a disturbance from outside the system, although such disturbances can be arbitrarily small. In the case of an excited atomic nucleus, the arbitrarily small disturbance comes from quantum vacuum fluctuations. A nucleus (or any excited system in quantum mechanics) is unstable, and can thus spontaneously stabilize to a less-excited system. This process is driven by entropy considerations: the energy does not change, but at the end of the process, the total energy is more diffused in spacial volume. The resulting transformation alters the structure of the nucleus. Such a reaction is thus a nuclear reaction, in contrast to chemical reactions, which also are driven by entropy, but which involve changes in the arrangement of the outer electrons of atoms, rather than their nuclei.
Some nuclear reactions do involve external sources of energy, in the form of collisions with outside particles. However, these are not considered decay. Rather, they are examples of induced nuclear reactions. Nuclear fission and fusion are common types of induced nuclear reactions.
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What makes a substance radioactive is the emission of energy from the nucleus which is the center of the atom. The nucleus is unstable so it lets out energy rays. Such rays can be Alpha particle rays, Gamma particle rays and Betta particle rays.
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Substances are radioactive because they have one or more neutrons than they should normally have.
Some good items to check for radioactivity are... smoke detectors (contain Americium, but DON'T take it apart to check it!) and if you can find an old analog watch with glow in the dark hands (contains deuterium), and Coleman lantern lamp bags (contain tritium).
👍 56 | 👎 -10
a million/2 existence is predicated on the possibility that anybody atom will decay. on an identical time as that is totally pretty much impossible to declare that a definite atom will decay while an excellent form of atoms are in touch, the share that decay strategies the calculated possibility. for this reason, the bigger the variety of atoms in touch, the nearer the measured fee strategies the calculated possibility.
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granite usually contains uranium,and gives off radon gas(how do you like your countertop now?)and coleman lantern lamp bags are also radioactive,don't hold one in your mouth while tying on the other.Grinding wheels for grinding metal are often radioactive...
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Originally Answered: Is a person radioactive after being x-rayed?
You are not radioactive after having a x-ray, but it sounds as if you had a nuclear medicine study.
We don't x-ray the thyroid gland, as this gland cannot be seen with x-ray alone. We used ultrasound (which involves no radiation) and nuclear medicine studies (which requires an injection of a radioisotope or swallowing a pill with a radiotracer).
The following is taken from a patient education site, regarding thyroid uptake and scans. You can also visit the site, to review the procedure, to ensure this is actually the study you had.....
"Through the natural process of radioactive decay, the small amount of radiotracer in your body will lose its radioactivity over time. In many cases, the radioactivity will dissipate over the first 24 hours following the test and pass out of your body through your urine or stool. You may be instructed to take special precautions after urinating, to flush the toilet twice and to wash your hands thoroughly. You should also drink plenty of water to help flush the radioactive material out of your body."
"No isolation or special precautions are needed after a thyroid scan."