What does the term half life mean and give the half life of a few substances?

Answer 1

The term half-life is applied to the time it takes half of a sample of a radioactive substance to decay. It really is as simple as that, but we'd better add a few things to make it clear. Let's look a bit more closely.

Radioactive materials or substance are unstable. That is, the nuclei of the atoms of radioactive materials are unstable, and they will want to undergo a change that will allow them to get to a more stable state. Radioactive decay is the term we apply to the nuclear decay of these materials.

Radioactive materials undergo decay at a given rate. If we have an atom of a radioactive material it will eventually decay, but we cannot be sure when a specific atom will actually decay. But we can do a statistical analysis of a large sample and get an accurate answer. By carefully measuring decay events and making statistical calculations, we have arrived at some very accurate figures for the half-lives of radioactive materials. They vary widely from the tiniest fractions of a second to many billions of years.

Here are some common radioisotopes and their half-lives:

• Uranium-238 has a half-life of 4.468 x 109 years. That's 4.468 billion years.
• Plutonium-239 has a half-life of 24,100 years.
• Cobalt-60 has a half-life of 5.2714 years.
• Radon-222 has a half-life of 3.8235 days.
• Carbon-14 has a half-life of 5,730 (+/- 40) years.

The half-life is the time it takes for one-half of something (usually a radioactive isotope) to decay.

Answer 2

The term half life applies to the period of time over which there is a 50% probability some single event will occur. It is used in many areas of science. An example is a capacitor discharging through a resistor or the decay of a radioactive isotope. It is a part of the law of natural decay.

Suppose we take the radioactive element Plutonium. This has a half life of 24,100 years. After this amount of time, since there is a 50-50 chance for each atom in this sample to decay, half of the atoms in a sample will have decayed in 24,100 years. After another 24,100 years, half of the half will have decayed meaning you still have a quarter of it left. After another 24,100 years, half of the quarter will have decayed meaning you still have an eighth of it left and so on.

Answer 3

The half life of a substance is the time it takes for half of the initial amount to decay or be removed. Some examples of half lives are: caffeine (5 hours), carbon-14 (5,730 years), and uranium-238 (4.5 billion years).