half-life

Half-Life and Radionuculide Review/Practice

by Chris Anderson

Isotope Recap

• Isotopes are elements with the same number of protons and different numbers of neutrons

• Different numbers of neutrons means different mass

• Mass = Protons + Neutrons

• Isotopes are named for their different mass number

• Ex. Carbon-12 has a mass of 12 and Carbon-13 has a mass of 13

Unstable Nuclei = Radiation

• Atoms with more than 84 protons are unstable

• Radioactivity is the emission of particles/energy from the nucleus

• The nucleus is too big

• This gradually makes more stable isotopes

Alpha

• Alpha decay releases 2 protons and 2 neutrons from the unstable nuclei

• This forms a new atom with an atomic number 2 fewer than the original

• The mass number also decreases by 4

• Alpha radiation is the least harmful

Beta

• Unstable nuclei result in a neutron splitting into an electron and a proton

• The proton stays in the nucleus

• The electron (Beta Particle) gets ejected

• This makes a new atom with an atomic number 1 greater than the original

• The mass stays the same

Gamma

• Unstable nuclei results in the release of high energy radiation

• Gamma rays are pure energy (no mass, no charge) & travels at the speed of light!

• It is usually released with alpha or beta particles

• The nucleus remains the same following this release

• 
  

Multiple Choice

If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.

• 1.25mg
• 1.25g
• 10g
• 10mg

Multiple Choice

The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?

• 3.0g
• 0.25mg
• 0.3g
• 0.25g

Multiple Choice

If the half-life of uranium-232 is 70 years, how many half-lives will it take for 10 g of it to be reduced to 1.25 g?

• 1 half-life
• 2 half-lives
• 3 half-lives
• 4 half-lives

Multiple Choice

The diagram shows 32 atoms.

16 of the Red are parent isotopes

16 of the Green are daughter isotopes

How many half-lives have occurred?

• 0

• 1

• 2

• 3

Multiple Choice

finish the equation

¹⁸¹₇₃Ta --> ____ + ¹⁸¹₇₄W

• ⁴₂He

• ⁰_-1e

• y

Multiple Choice

finish the equation

²²⁶₈₈Ra --> ____ + ²²⁶₈₈Ra

• ⁴₂He

• ⁰_-1e

• y

Multiple Choice

Identify the type of nuclear decay shown here

²¹⁴₈₃Bi → ⁰_-1e + ²¹⁴₈₄Po

• alpha

• beta

• gamma

Multiple Choice

Solve this equation.

₈₅²⁰⁹At = ___ + ₂⁴He

• ₈₃²⁰⁵Bi

• ₈₆²⁰⁹Rn

• ₈₁²⁰⁷Tl

• ₈₅²⁰⁸At

Multiple Choice

Finish this equation

²⁰⁹₈₃Bi--> _{_______ +} ²⁰⁵₈₁Tl

• ⁴₂He

• ⁰_-1e

• y

Multiple Choice

What type of nuclear decay is shown here

¹³⁷₅₆Ba →→ ¹³⁷₅₆Ba + γ rays

• alpha

• beta

• gamma

Multiple Choice

What type of decay is shown here

²³⁸₉₂U ---> ²³⁴₉₀Th + ⁴₂He.

• alpha

• beta

• gamma

Multiple Choice

Solve this equation for.

₆¹⁴C = ___ + _-1⁰e

• ₄¹⁰Be

• ₇¹⁴N

• ₂¹⁰He

• ₆¹³C

Multiple Choice

Solve this equation.

₈₈²²⁶Ra = ___ + ₂⁴He

• ₈₆²²²Rn

• ₈₉²²⁶Ac

• ₈₄²²⁴Po

• ₈₈²²⁵Ra

Multiple Choice

If we start off with element ⁵⁰₂₄X after an gamma decay we get an element(product) that looks like...

• ⁵¹₂₄X

• ⁵⁰₂₃X

• ⁵⁰₂₄X

• ⁵⁰₂₅X

Multiple Choice

Two or more nuclei combine to form one larger nucleus in the process of nuclear _____.

• Fusion
• Fission
• Tracing
• Decay

Multiple Choice

A nuclear reaction where a nucleus splits into two smaller nuclei is... 

• Fission
• Fusion
• Gamma decay
• Beta decay

Multiple Choice

What is another name for an alpha particle?

• electron
• x-ray
• hydrogen nucleus
• helium nucleus

Multiple Choice

The least penetrating form of radiation is...

• alpha
• beta
• gamma
• neutron

Multiple Choice

The charge on a gamma particle is...

• -1
• 0
• +1
• +2

Multiple Choice

What particle completes this reaction?

• alpha particle
• beta particle
• gamma particle
• neutron

Multiple Choice

What type of decay is being illustrated in following picture? 

• beta decay
• alpha decay 

Multiple Choice

You have 100 grams of radioactive C-14. The half life of C-14 is 5730 years. 
How many grams are left after 1 half life? 

• 100 grams
• 25 grams
• 2 grams
• 50 grams

Multiple Choice

What is Half-life?

• The amount of time it takes for some of the nuclei in a sample of the isotope to decay
• The amount of time it takes for half the electrons in a sample of the isotope to decay
• The amount of time it takes for half the nuclei in a sample of the isotope to decay
• the amount of time it takes to double the nuclei in a sample of the isotope to decay

Multiple Choice

The diagram shows 32 atoms

32 of the Red are the parent isotope

0 of the atoms are daughter isotopes

How many half-lives have occurred?

• 0

• 1

• 2

• 3

Multiple Choice

Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained. If it takes 10 minutes to set up an experiment using barium-122, how much barium-122 will be left when the experiment begins?

• 0.25g
• 2.5g
• 25g
• 80g

Multiple Choice

The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?

• 3.0g
• 0.25mg
• 0.3g
• 0.25g

Multiple Choice

After 4 half-lives, 1g of a sample of Krypton-85 remains unchanged.  What was the original mass of the sample?

• 16g
• 32g
• 0.0625g
• 4g

Multiple Choice

What is the half-life of iodine-131?

• 32 days
• 8 days
• 16 days
• 24 days

Multiple Choice

If one-fourth of the carbon-14 is remaining then how many half-lives have passed?

• 1
• 2
• 3
• 4

Multiple Choice

The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed?

• 100.0g
• 50.0g
• 12.5g
• 8.5g

Multiple Choice

The half life of iodine-131 is 8 days. What fraction of an iodine-131 sample will remain after 40 days?

• 1/2
• 1/64
• 1/5
• 1/32

Multiple Choice

Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained. If it takes 10 minutes to set up an experiment using barium-122, how much barium-122 will be left when the experiment begins?

• 0.25g
• 2.5g
• 25g
• 80g

Multiple Choice

Gamma rays damage human cells/tissue.

• True
• False

Multiple Choice

When an element loses protons, its __________changes.

• protonic number
• electronic number
• neutronic number
• atomic number