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# the percentage of radioactive atoms that decay during one half-life is always the same.

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### James

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get the percentage of radioactive atoms that decay during one half-life is always the same. from EN Bilgi.

## Can the decay half

Yes, the decay half-life of a radioactive material can be changed. Radioactive decay happens when an unstable atomic nucleus spontaneously changes ...

## Can the decay half-life of a radioactive material be changed?

Category: Physics

Published: April 27, 2015

Yes, the decay half-life of a radioactive material can be changed. Radioactive decay happens when an unstable atomic nucleus spontaneously changes to a lower-energy state and spits out a bit of radiation. This process changes the atom to a different element or a different isotope. Since radioactive decay is a spontaneous event, you may think that the half-life of the decay process is completely fixed and cannot be altered by outside influences. However, this statement is not completely true. Public Domain Image, source: Christopher S. Baird.

First of all, it is worth pointing out that the time when an individual radioactive atom decays is completely random. It is impossible to predict when an individual radioactive atom will decay. The half-life of a certain type of atom does not describe the exact amount of time that every single atom experiences before decaying. Rather, the half-life describes the average amount of time it takes for a large group of amounts to reach the point where half of the atoms have decayed.

The half-life of a radioactive material can be changed using time dilation effects. According to relativity, time itself can be slowed down. Everything that experiences time can therefore be given a longer effective lifetime if time is dilated. This can be done in two ways. Traveling at a speed close to the speed of light causes time to slow down significantly, relative to the stationary observer. For instance, a number of radioactive atoms shot through a tube at high speed in the lab will have their half-life lengthened relative to the lab because of time dilation. This effect has been verified many times using particle accelerators. Time can also be dilated by applying a very strong gravitational field. For instance, placing a bunch of radioactive atoms near a black hole will also extend their half-life relative to the distant observer because of time dilation.

The half-life of radioactive decay can also be altered by changing the state of the electrons surrounding the nucleus. In a type of radioactive decay called "electron capture", the nucleus absorbs one of the atom's electrons and combines it with a proton to make a neutron and a neutrino. The more the wavefunctions of the atom's electrons overlap with the nucleus, the more able the nucleus is to capture an electron. Therefore, the half-life of an electron-capture radioactive decay mode depends slightly on what state the atom's electrons are in. By exciting or deforming the atom's electrons into states that overlap less with the nucleus, the half-life can be reduced. Since the chemical bonding between atoms involves the deformation of atomic electron wavefunctions, the radioactive half-life of an atom can depend on how it is bonded to other atoms. Simply by changing the neighboring atoms that are bonded to a radioactive isotope, we can change its half-life. However, the change in half-life accomplished in this way is typically small. For instance, a study performed by B. Wang et al and published in the European Physical Journal A was able to measure that the electron capture half-life of beryllium-7 was made 0.9% longer by surrounding the beryllium atoms with palladium atoms.

In addition to altering the chemical bonds, the half-life can be altered by simply removing electrons from the atom. In the extreme limit of this approach, all of the electrons can be ripped off of a radioactive atom. For such an ion, there are no longer any electrons available to capture, and therefore the half-life of the electron capture radioactive decay mode becomes infinite. Certain radioactive isotopes that can only decay via the electron capture mode (such as rubidium-83) can be made to never decay by ripping off all the electrons. Other types of radioactive decay besides electron capture have also been found to have the decay half-life depend on the state of the surrounding electrons, but the effects are smaller. The change in half-life due to changing the electron environment is generally very small, typically much less than 1%.

Lastly, the half-life of a radioactive material can be changed by bombarding it with high-energy radiation. This should not come as a surprise since radioactive decay is a nuclear reaction, and inducing other nuclear reactions at the same time as the decay can interfere with it. However, at this point, you don't really have stand-alone radioactive decay. Rather, you have nuclear reaction soup, so this approach may not really count as "changing the half-life".

When reference books list values for the half-life of various materials, they are really listing the half-life for the material when its atoms are at rest, in the ground state, and in a particular chemical bonding configuration. Note that most changes to the half-life of radioactive materials are very small. Furthermore, large changes to a half-life require elaborate, expensive, high-energy equipment (e.g. particle accelerators, nuclear reactors, ion traps). Therefore, outside of specialized labs, we can say that as a good approximation radioactive decay half-lives don't change. For instance, carbon dating and geological radiometric dating are so accurate because decay half-lives in nature are so close to constant.

Source : www.wtamu.edu

## 2.6 Half

Unstable nuclei decay in a very specific way, following what is called a first-order process. In a first-order decay process, the rate of the decay depends directly on the number of radioactive … ## 2.6 Half-lives and the Rate of Radioactive Decay

Last updated Jun 19, 2020

2.5 The Belt of Stability - Predicting the Type of Radioactivity

2.7 Mass Defect - The Source of Nuclear Energy

Skills to Develop

To know how to use half-lives to describe the rates of first-order reactions

Radioactivity, or radioactive decay, is the emission of a particle or a photon that results from the spontaneous decomposition of the unstable nucleus of an atom. The rate of radioactive decay is an intrinsic property of each radioactive isotope that is independent of the chemical and physical form of the radioactive isotope. The rate is also independent of temperature. Because there are so many unstable nuclei that decay, we need a method to describe and compare the rates at which these nuclei decay. One approach to describing reaction rates is based on the time required for the number of unstable nuclei to decrease to one-half the initial value. This period of time is called the half-life of the process, written as t1/2. Thus the half-life of a nuclear decay process is the time required for the number of unstable nuclei to decrease from [A]0 to 1/2[A]0.

1 100% 2 =50% 100%2=50% 1 2 (100%)=50% 12(100%)=50% 2 50% 2 =25% 50%2=25% 1 2 ( 1 2 )(100%)=25% 12(12)(100%)=25% 3 25% 2 =12.5% 25%2=12.5% 1 2 ( 1 2 )( 1 2 )(100%)=12.5%

12(12)(12)(100%)=12.5%

n 100% 2 n 100%2n ( 1 2 ) n (100%)= ( 1 2 ) n % (12)n(100%)=(12)n%

As you can see from this table, the amount of reactant left after n half-lives of a first-order reaction is (1/2)n times the initial concentration.

For a first-order reaction, the concentration of the reactant decreases by a constant with each half-life and is independent of [A].

For a given number of atoms, isotopes with shorter half-lives decay more rapidly, undergoing a greater number of radioactive decays per unit time than do isotopes with longer half-lives. The half-lives of several isotopes are listed in Table 14.6, along with some of their applications.

Table: Half-Lives and Applications of Some Radioactive Isotopes

2 2

hydrogen-3 (tritium)

12.32 yr biochemical tracer carbon-11 20.33 min

positron emission tomography (biomedical imaging)

carbon-14 5.70 × 103 yr dating of artifacts sodium-24 14.951 h

cardiovascular system tracer

phosphorus-32 14.26 days biochemical tracer potassium-40 1.248 × 109 yr dating of rocks iron-59 44.495 days

cobalt-60 5.2712 yr

technetium-99m* 6.006 h biomedical imaging iodine-131 8.0207 days

thyroid studies tracer

uranium-238 4.468 × 109 yr

dating of rocks and Earth’s crust

americium-241 432.2 yr smoke detectors Note

Radioactive decay is a first-order process.

Example 1 1

If you have a 120 gram sample of a radioactive element, how many grams of that element will be left after 3 half-lives have passed?

SolutionGiven: mass of radioactive sample of an element, number of half-livesAsked to Solve For: mass of radioactive element after so many half-livesSolve:

All radioactive samples lose half of their mass after each half-life. Thus, one solution is to calculate the mass after each half-life. (This method only works if you are asked to solve for a whole number of half-lives). Let the passing of time equal to one half-life be represented by and arrow, →. Then the solution is:

120 g → 60 g → 30 g → 15 g

If you want to solve for any number of half-lives, including fractional half-lives, then you use the equation: amount remaining =

( 1 2 ) n (amountatstart)

(12)n(amountatstart)

, where n= number of half-lives. Then the solution is:

amount remaining = ( 1 2 ) 3 (120g)=15g (12)3(120g)=15g Exercise 1 1

If you have a 300. gram sample of a radioactive element, how many grams of that element will be left after 4.30 half-lives have passed?

Exercise 2 2

A certain radioactive nuclide has a half-life of 5.25 days. If you start with 100. grams of this nuclide, how many grams of the nuclide will be left after 20.0 days?

In our earlier discussion, we used the half-life of a first-order reaction to calculate how long the reaction had been occurring. Because nuclear decay reactions follow first-order kinetics and have a rate constant that is independent of temperature and the chemical or physical environment, we can perform similar calculations using the half-lives of isotopes to estimate the ages of geological and archaeological artifacts. The techniques that have been developed for this application are known as radioisotope dating techniques.

Source : chem.libretexts.org

## ch 11

3.0 1 Review

How is the atomic number of an atom determined?

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counting the number of protons in the nucleus

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Which process is not a common form of natural radioactive decay?

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nuclear fission

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1/20 Created by ChelseaPotter90 radiometric dating

### Terms in this set (20)

How is the atomic number of an atom determined?

counting the number of protons in the nucleus

Which process is not a common form of natural radioactive decay?

nuclear fission

Which material, principle, or process enables a method of numerical dating?

Which is an example of radioactivity that occurs when a neutron is converted to a proton and an electron is emitted from the nucleus?

emission of a beta particle

After four half-lives of decay, what is the ratio of radioactive parent isotope to stable daughter isotope?

1:15

A radioactive element undergoes decay via the loss of two alpha particles to form a stable daughter isotope. Following the decay, what would the atomic number of this newly created stable isotope be?

The atomic number of the daughter isotope would be four units less than the original parent isotope.

When a radioactive isotope decays by electron capture, the electron ________.

combines with a proton in the nucleus; the atomic number of the daughter is one less than the parent

The radioactive isotope, potassium-40, has argon-40 as a daughter product.

True

Which of the following includes all common types of radioactive decay?

alpha particle emission, beta particle emission, electron capture

Which of the following statements regarding radioactive decay is true?

More daughter products accumulate over time.

If one half-life has lapsed, what is the radioactive parent to stable daughter isotope ratio?

75:25

Radioactive decay in mineral shows that two half-lives have elapsed, giving an age of approximately 1.4 billion years. Using the table in the video as a reference, what is the correct radioactive parent and stable daughter isotope pair?

U235, Pb207

After two half-lives, there is no longer any of the original radioactive material remaining.

False

The percentage of radioactive atoms that decay during one half-life is always the same.

True

A zircon in a lava flow is going through radioactive decay. By the time a sample is collected by a geologist, only six percent of its original parent material still remains. How many half-lives has the zircon experienced?

4 half-lives

After three half-lives, one-ninth of an original radioactive parent isotope remains, and eight-ninths has decayed into the daughter isotope.

False

Which of the following is not a very long-lived, radioactive isotope?

C-14

Which of the following radioactive isotopes is used to date very recent events?

carbon-14

The half-life of carbon-14 is about 6000 years. Assume that a sample of charcoal formed by burning of living wood 15,000 years ago. How much of the original carbon-14 would remain today?

between one-fourth and one-eighth

Numerical dates based on radioactivity are very important for studying Precambrian geologic history because fossils are rare or absent.

True

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### Verified questions

CHEMISTRY

For each of the following atomic numbers, use the periodic table to write the formula (including the charge) for the simple ion that the element is most likely to form in ionic compounds. 7

How did the Precambrian atmosphere become nitrogen enriched?

Verified answer CHEMISTRY Indicate whether \Delta G ΔG

in creases, decreases, or does not change when the partial pressure of

H_2 H 2 ​

is increased in each of the following reactions:

2 \mathrm { H } _ { 2 } ( g ) + \mathrm { C } _ { 2 } \mathrm { H } _ { 2 } ( g ) \longrightarrow \mathrm { C } _ { 2 } \mathrm { H } _ { 6 } ( g )

2H 2 ​ (g)+C 2 ​ H 2 ​ (g)⟶C 2 ​ H 6 ​ (g) Verified answer CHEMISTRY

Long before scientists understood the properties of elements and compounds, artists used chemistry to create pigments from natural materials. Table gives some examples of such pigments used in ancient times. Common Artists’ Pigments Used in Early Times.

\begin{matrix} \text{Common Name} & \text{Chemical Identity} & \text{Comments}\\ \text{Charcoal} & \text{elemental carbon} & \text{produced by dry}\\ \text{ } & \text{(carbon black)} & \text{distillation of wood in a closed vessel}\\ \text{Egyptian } & \text{calcium copper } & \text{crystalline compound}\\ \text{blue} & \text{tetrasilicate,} & \text{containing some glass}\\ \text{ } & \ {\mathrm{CaCuSi}_{4} \mathrm{O}_{10}} & \text{impurity}\\ \text{Indigo} & \text{indigotin,} & \text{derived from different}\\ \text{ } & \ {\mathrm{C}_{16} \mathrm{H}_{10} \mathrm{N}_{2} \mathrm{O}_{2}} & \text{plants of the genus Indigofera}\\ \text{Iron } & \ {\mathrm{Fe}_{2} \mathrm{O}_{3}} & \text{in continuous use in all geographic}\\ \text{oxide red} & \text{ } & \text{regions and time periods}\\ \text{Verdigris} & \text{dibasic acetate} & \text{other copper compounds,}\\ \text{ } & \text{of copper,} & \text{including carbonate, are also}\\ \text{ } & \ {\mathrm{Cu}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{2} \cdot 2 \mathrm{Cu}(\mathrm{OH})_{2}} & \text{called verdigris}\\ \end{matrix}

Source : quizlet.com

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James 4 day ago

Guys, does anyone know the answer?