# If a sample of a radioactive isotope has a half life of 1 day how much remains at the end of the second day and at the end of the third day?

If a sample of a radioactive isotope has a half life of 1 day, then there will be one half of the original sample left after one day, and one quarter (one half of one half) left after two days, and one eighth (one half of one half of one half) after three days.

### What is the half life of radioisotope?

Half life is the time taken for approximately half of the available nuclei in a sample of radioactive material to decay into something else. It's a characteristic of the isotope, for example, the half life of the isotope of iodine, I131 is 8.08 days. Half lives can vary from fractions of a second to thousands of years.

### How much of the original sample will be left at the end of the second day if a sample of radioactive isotope has a half life of 1 day?

That's two half lives. At the end of the first day, half the original material has decayed. At the end of the second day, half of what's left, or one quarter, more will have decayed. So one quarter of the original material will be left. Note that the other three quarters is probably "still there", it'll just be a different nuclide.

### What is meant by the half-life of a radioactive isotope?

A half-life is the time it takes for half the original quantity of a given radioisotope to decay. If we are given a sample of one kind of radioactive material, the time it takes for half of it to undergo radioactive decay is the half-life of that radioisotope. It's a statistically derived figure, but scientists have arrived at some very accurate figures to denote the half-life of different radioactive isotopes. The half-life of an unstable…

### What is the average atomic mass of an element is the average atomic masses of what kind of isotopes?

### How long will it take for half of the atoms in that sample to decay?

Half the atoms in a sample of radioactive material will decay in a certain amount of time, and that length of time is called a half life. Here is the same idea: the half life of a radioactive material is the time it takes for half the atoms in a given sample of that radioactive material to decay. As one might guess, the half life of a given material will be different than that for…

### What is the formula to calculate the half-life of a radioactive isotope?

The following formula can be used to calculate half-life (t1/2): t1/2 = (t ln 1/2)/(ln mf / mi) t = time that has passed mf = the final or remaining mass of undecayed sample mi = the initial or original mass of undecayed sample (The fraction mf / mi is of course equivalent to the fraction of undecayed sample remaining, in case you are given the fraction remaining rather than specific masses.) Note: You can…

### Explain what percentage of the parent element will decay into the daughter element through the process of radioactive decay during each of the first 3 half lives?

During the first half life, half of the radioactive substance decays. During the second half life, half of what is left decays; since this is half of the original amount, a quarter of the original radioactive material decays away, and a quarter remains. During the third half life, half of what is left decays; since this is a quarter of the original amount, an eighth of the original radioactive material decays away, and an eighth…

### What is the half-life of an isotope if 200 g of a 800 g sample of the isotope remains after 4.0 years?

The ratio of mass remaining in going from 800 g to 200 g is 0.25. By inspection, this is two half-lives. Remember that at the first, second, third, and fourth half-life, you have 0.5, 0.25, 0.125, and 0.0625 of the original material left. This means the half life is 2.0 years. Formally, the equation for half-life is ... AT = A0 2(-T/H) ... Where A0 is the original activity, AT is the activity after some…

### How many of each elementary particles are contained in the hydrogen atom?

The most common isotope of hydrogen contains one each of proton and electron and no neutron per atom. This is the only stable atom with no neutrons. The second most common isotope of hydrogen, which is sometimes given the special name "deuterium", contains one each of proton, electron, and neutron. A radioactive isotope of hydrogen with the special name "tritium" contains one each of proton and electron together with two neutrons.

### How many neutrons does calcium have?

The most common isotope of calcium (40Ca) has 20 neutrons. You can find this out by subtracting the number of protons (atomic number, 20), from the total AMU's of 40. About 96% of calcium on Earth is calcium-40. Calcium also has eight other isotopes, 41Ca through 48Ca, five of which are radioactive. The second-most prevalent stable isotope is 44Ca which is about 2% of all calcium.

### What is the law of decay?

The rate of decay at any time (i.e. no. of atoms that disintegrate per second) is directly proportional to the number of radioactive atoms present in the sample at that time.This is known as decay law. rate of disintegration = -dN/dt ,according to decay law -dN/dt is directly proportional to N, where N is the no. of radioactive atoms present at the instant of disintegration.

### Why does a sample of radioactive element tend to lose mass gradually?

It actually loses very little mass due to the release of beta particles (electrons and positrons) as the element undergoes radioactive decay. But the loss of alpha particles (He nuclei) represents considerable loss of mass. Depending on the element, the time scale for the loss of mass can vary enormously, from fractions of a second to thousands of years.

### What relationship do atomic numbers and radioactivity have?

There is no relationship between atomic number and radioactivity. Atomic nuclei, according to Bohr's model, are comprised of protons and neutrons. The atomic number is the number of protons in the nucleus. The number of neutrons bound in the nucleus does not change the atomic number, but instead determines the isotope. There are many isotopes for each atomic number. The radioactive decay constant (denoted as lambda) carries the units [1/s] and can be thought of…

### Do all radioactive isotopes follow the half-life single rate or are there those that decay at multiple rates throughout their decay?

In general, a radioactive substance decays at a constant rate throughout time. That is not to say that the same number of decays occur per unit time. They cannot, and this is because the sample is shrinking as radioactive decay "claims" more and more of it. The decays per second is decreasing. But the rate of decay remains constant. There are some instances where slight changes in decay rates of a couple of different radioactive…

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

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…

### How does the half life of a radioactive isotope affect the usefulness of that isotope in radioactive dating?

The half-life of an isotope is only useful in dating if the half-life is a reasonable fraction of the actual age. For example, a half-life in the range of days or even a few years is meaningless if the sample is several thousand years old. On the other hand, a half-life in the hundreds of thousands of years is also not useful if the sample is, say, 15,000 years old. All of this has to…

### Do labs keep urine after they test it?

There are single-sample tests and split-sample tests. If you've got a split-sample test, the second half of the sample goes into the freezer for six months regardless. For single-sample and the other part of a split-sample test, they retain the sample if it tests positive, but if it tests negative they normally dump it.

### What is Dependent Sampling method?

Data gathered in two different samples in such a way that there is a matching of the first sample data drawn and a corresponding data value in the second sample data. For example, compare two sample means, one for the first exam of the semester and the second for the second exam of the semester, match via the student taking each test.

### What is the relationship between half-life and radioactivity?

If you know the half life of an isotope and the amount of it present, it is possible to calculate the numbers of decay events per second in the mass. This does not provide all the information about radioactivity, because it does not provide information about the type of decay. The missing information includes the type of emission (alpha, beta, gamma, fission, etc.), the energy of the emitted particle or particles, and the energy imparted…

### What happens to radioactive materials if you do not use them?

That depends on the radioactive material. But whether you use it or not, the radioactive material will decay into other elements over the course of time. The time it takes for half of the material to decay into something else is called the "half-life". The more radioactive the substance is, the faster it decays. The half-life of a radioactive element can be measured from fractions of a second to billions of years.

### I tested positive for a urine test will same sample test positive 19 days later?

Split sample drug test? It depends. If what you're asking is, "I was positive because I was doing drugs; are the drugs going to leave my sample after 19 days?" the answer is that you'll still be positive. They freeze the second part of your sample, so there's no way anything could get out of it--and the drug metabolites in the sample wouldn't leave the sample anyway. If, OTOH, you're asking "I got a false…

### The mass of a sample of water is unchanged when it expands?

Yes, the mass of a sample of water remains unchanged when it expands. This is because only its density and volume vary with temperature. As the temperature increases, two dependent changes occur: the volume of the water increases and the density decreases. These two changes happen in correlation with each other such that the mass remains exactly the same. A second way of thinking about this problem is on a molecule scale. When heating water…