Table of Contents

- 1 What percentage of an original sample of iodine-131 will remain after 64 days if iodine-131 has a half-life of 8 days?
- 2 What is the half-life of iodine-131 if after 24 days?
- 3 How do you find the half life of something?
- 4 What percent of the original sample remains?
- 5 How is iodine-131 formed?
- 6 What is the activity of a radioactive substance?
- 7 How does iodine 131 decay into xenon 131?
- 8 Which is an unstable radioisotope of iodine used for hyperthyroidism?

## What percentage of an original sample of iodine-131 will remain after 64 days if iodine-131 has a half-life of 8 days?

It decays by beta particle emission into xenon-131. After eight days have passed, half of the atoms of any sample of iodine-131 will have decayed, and the sample will now be 50% iodine-131 and 50% xenon-131.

## What is the half-life of iodine-131 if after 24 days?

8 days

The half-life of iodine-131 is 8 days. Since the half-life is 8 days, 24 days corresponds to 3 half-lives.

**What is the ½ life of iodine-131?**

The 131I isotope has a half-life of 8 days and emits γ radiation and β particles. Given orally, it is concentrated in the thyroid, where the β particles destroy the gland. Symptoms of hyperthyroidism begin to improve in a few days to a few weeks, but 2 to 3 months are often required for a complete effect.

**How do you calculate the activity of a radioactive sample?**

- Activity = λN.
- = (0.693/8 days) x (1/86,400 sec/day) x (3 x 1017 atoms)
- = 3 x 1011 atoms/sec I-131.
- = 3 x 1011 dps I-131.

### How do you find the half life of something?

So, if a problem asks you to calculate an element’s half-life, it must provide information about the initial mass, the quantity left after radioactive decay, and the time it took that sample to reach its post-decay value. Therefore, its half-life is t1/2=98.012.7=7.72 years .

### What percent of the original sample remains?

After three half-lives 1/8 (12.5%) of the original sample remains. A half-life is the amount of time it takes for one half of a sample to undergo radioactive decay. Therefore, after one half-life, 1/2 of the sample remains.

**What happens during one half-life of a radioactive isotope?**

Radioactive decay reduces the number of radioactive nuclei over time. In one half-life t1/2, the number decreases to half of its original value. Half of what remains decay in the next half-life, and half of those in the next, and so on.

**What is a 1/2 life?**

Half-life (t1/2) is defined as the amount of time required for the drug concentration measured in plasma (or other biological matrices) to be reduced to exactly half of its starting concentration or amount. After IV dosing, the drug concentrations in plasma decline due to both elimination and distribution [15].

#### How is iodine-131 formed?

Iodine-131 is an artificially produced fission by-product resulting from nuclear weapons, above-ground nuclear testing, and nuclear reactor operations. Iodine-131 is found in the gaseous and liquid waste streams of nuclear power plants, but is not released to the environment during normal reactor operations.

#### What is the activity of a radioactive substance?

Activity, in radioactive-decay processes, the number of disintegrations per second, or the number of unstable atomic nuclei that decay per second in a given sample.

**How is activity concentration calculated?**

Concentration activity in units of Bq/g, so you divide activity by the mass in g of the substance containing the isotope. t is the total counting time in the example its equal 2000 seconds.

**How does iodine 131 get into the thyroid?**

Iodine-131 is readily absorbed by the follicular cells of the thyroid gland via the sodium/iodine symporter. As the atoms of iodine-131 accumulate in the thyroid, they eventually undergo a two-step radioactive decay process that releases high energy electrons and electromagnetic radiation in the form of gamma rays.

## How does iodine 131 decay into xenon 131?

These highly energetic electrons can penetrate and damage surrounding tissue within 2 mm from the source of emission. Roughly 90 percent of iodine-131 atoms decay into xenon-131 via the decay scheme depicted in Figure 1.

## Which is an unstable radioisotope of iodine used for hyperthyroidism?

Iodine-131 is an unstable radioisotope of iodine that is commonly used for the treatment of hyperthyroidism caused by Grave’s disease. Iodine-131 is readily absorbed by the follicular cells of the thyroid gland via the sodium/iodine symporter.

**How is the radioactivity of iodine-131 determined?**

The radioactivity of iodine-131. Iodine-131 decays into xenon-131 by a first order process, which means that the rate of decay is directly proportional to the concentration of iodine-131. The half-life, the time required for one half of a given amount of a substance to decay, of a first order process is however independent of the concentration.