If it is full to the brim, it is unstable, and some water is certain to slosh out. All Rights Reserved. Menu About Contacts Directions. Latest Issue: June All Issues ». People ask us questions and we try to answer them. In beta decay, a stream of electrons, called beta particles, are ejected from the parent, and a neutron in the nucleus is converted into a proton.
The mass number of the new nucleus is the same, but the atomic number increases by one. In gamma decay, the atomic nucleus releases excess energy in the form of high-energy photons electromagnetic radiation. The atomic number and mass number remain the same, but the resulting nucleus assumes a more stable energy state. A radioactive isotope is one that undergoes radioactive decay.
The term "stable" is more ambiguous, as it applies to elements that don't break apart, for practical purposes, over a long span of time. This means stable isotopes include those that never break, like protium consists of one proton, so there's nothing left to lose , and radioactive isotopes, like tellurium , which has a half-life of 7.
Radioisotopes with a short half-life are called unstable radioisotopes. You might assume that a nucleus in stable configuration would have the same number of protons as neutrons. For many lighter elements, this is true. For example, carbon is commonly found with three configurations of protons and neutrons, called isotopes. The number of protons does not change, as this determines the element, but the number of neutrons does: Carbon has six protons and six neutrons and is stable; carbon also has six protons, but it has seven neutrons; carbon is also stable.
However, carbon, with six protons and eight neutrons, is unstable or radioactive. The number of neutrons for a carbon nucleus is too high for the strong attractive force to hold it together indefinitely. But, as you move to atoms that contain more protons, isotopes are increasingly stable with an excess of neutrons. This is because the nucleons protons and neutrons aren't fixed in place in the nucleus, but move around, and the protons repel each other because they all carry a positive electrical charge.
The neutrons of this larger nucleus act to insulate the protons from the effects of each other. The ratio of neutrons to protons, or N:Z ratio, is the primary factor that determines whether or not an atomic nucleus is stable.
A particular radioactive atom can and will decay at any time. The "lifetime" of a radioactive isotope is not a description of how long a single atom will survive before decaying.
Rather, it is a description of the average amount of time it takes for a significant portion of a group of radioactive atoms to decay. A characteristic lifetime does not come about by the progression of internal machinery, but by the statistical behavior of a large group of atoms governed by probability.
An analogy may be helpful. A standard six-sided die will show a single number between "1" and "6" when rolled. Let us agree that when we roll a "6", we smash the die to pieces and the game is over for that particular die. We begin rolling the die and get a "3", and then a "1" and then a "5". Next we roll a "6" and destroy the die as agreed upon. Since the die was destroyed after four rolls, we say that this particular die had an individual lifetime of four rolls.
Now we get a new die and repeat the game. For this die, we roll a "2", then a "1", then "4", "3", "1", "5", and then finally a "6". Radioactivity is the release of energy from the decay of the nuclei of certain kinds of atoms and isotopes. Atomic nuclei consist of protons and neutrons bound together in tiny bundles at the center of atoms.
Radioactive nuclei are nuclei that are unstable and that decay by emitting energetic particles such as photons, electrons, neutrinos, protons, neutrons , or alphas two protons and two neutrons bound together. Some of these particles are known as ionizing particles.
These are particles with enough energy to knock electrons off atoms or molecules.
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