The Solid Earth - Chapter 9: Radioactivity and Radiometric Dating Flashcards

1
Q

We know that the earth is 4.6B years old and that the dinosaurs became extinct about ___ years ago

A

66 million

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2
Q

True or false: a neutron is technically a proton and electron combined

A

True

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3
Q

In some isotopes, the ____ is unstable

A

nucleus

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4
Q

What is an isotope?

A

An atom with different numbers of neutrons in the nucleus

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5
Q

This results when the nuclei spontaneously break apart (decay)

A

radioactivity

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6
Q

Name three types of radioactive decay

A

Alpha particles emitting from the nucleus
Beta particle or electron given off from nucleus
Electron captured by nucleus (combined with proton and forms neutron)

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7
Q

The radioactive isotope is referred to as the ____

A

parent

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8
Q

The isotopes resulting from the decay of the parent are termed the ____

A

daughter

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9
Q

What is the process called whereby radioactivity helps calculate the age of rocks and minerals containing particular radioactive isotopes

A

radiometric dating

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10
Q

Each radioactive isotope used for dating has been decaying at a ___ rate since the formation of the rocks in which it occurs and the products of decay have been accumulating at a corresponding rate

A

fixed

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11
Q

The time required for one half of the nuclei in a sample to decay which is a common way of expressing the rate of radioactive disintegration

A

half life

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12
Q

When the quantities of parent and daughter are ___ (1:1) we know that one half life has transpired.

A

equal

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13
Q

How do we know that two half lives have passed?

A

One quarter of parent remains and three quarters have decayed to the daughter product (ratio 1:3)

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14
Q

After three half lives, the ratio of parent to daughter atoms is ___

A

1:7

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15
Q

True or false: if the half life of a radioactive isotope is known and the parent/daughter ratio can be determined the age of the sample can be calculated

A

True

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16
Q

As the percentage of radioactive parent atoms ____, the proportion of stable daughter atoms ____

A

declines

rises

17
Q

What is something used to make sure that radiometric dates are meaningful?

A

cross checks

18
Q

What radioactive isotope is used to date very recent events?

A

Carbon - 14

19
Q

What is another name for Carbon-14?

A

radiocarbon

20
Q

What is the half life of Carbon-14?

A

5730 years

21
Q

True or false: all organisms contain a small amount of carbon-14

A

True

22
Q

When a plant or animal dies, the amount of carbon-14 gradually decreases as it decays to ___

A

nitrogen

23
Q

Describe Carbon-12

A

the stable and most common isotope of carbon