The ratio of neutrons to protons, or N:Z ratio, is the primary factor that determines whether or not an atomic nucleus is stable. There are also what are called magic numbers, which are numbers of nucleons either protons or neutrons that are especially stable.
If both the number of protons and neutrons have these values, the situation is termed double magic numbers. You can think of this as being the nucleus equivalent to the octet rule governing electron shell stability.
The magic numbers are slightly different for protons and neutrons:. To further complicate stability, there are more stable isotopes with even-to-even Z:N isotopes than even-to-odd 53 isotopes , than odd-to-even 50 than odd-to-odd values 4. One final note: Whether any one nucleus undergoes decay or not is a completely random event. The half-life of an isotope is the best prediction for a sufficiently large sample of the elements.
It can't be used to make any sort of prediction on the behavior of one nucleus or a few nuclei. Can you pass a quiz about radioactivity? Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile. Select personalised ads.
Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Anne Marie Helmenstine, Ph. If the pail is nearly empty, it is stable, and water will not slosh out. 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.
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". This die therefore had an individual lifetime of seven rolls. When we repeat this game for many dice, we discover that the individual lifetime of a particular die can be anything from one roll to hundreds of rolls.
However, if we average over thousands of individual lifetimes, we find that the dice consistently have an average lifetime of about six rolls. Since an individual die has no internal machinery telling it to show a "6" after a certain number of rolls, the individual lifetime of a die is completely random.
However, since the random events are governed by probabilities, we can experimentally find a fixed characteristic average lifetime of a group of dice by averaging over a large ensemble of dice. We can also mathematically find the average lifetime by calculating probabilities. For the die, there are six possible outcomes to a single roll, each with equal probability of occurring.
Therefore, the probability of rolling a "6" and destroying the die is 1 out of 6 for every roll. For this reason, we expect it to take six rolls on average to roll a 6 and destroy the die, which is just what we found experimentally. The dice do not have a predictable average lifetime because they age, but because they experience probabilistic events.
In the same way, atoms do not age and yet we can identify a meaningful decay lifetime because of the probabilities. Topics: aging , atom , atoms , decay , life , lifetime , probability , radioactive decay , radioactivity. Artistic illustration of radioactive beta decay.
0コメント