Isotopes and standards Flashcards

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1
Q

What is an isotope?

A

atoms with an equal number of protons and electrons but different number of neutrons – making them either heavy or light

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2
Q

What is the proportion of different carbon isotopes?

A

C12= 98.9%
C13= 1.1%
C14= <0.0001%

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3
Q

What is the ratio of C13/C12?

A

0.011

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4
Q

What is the stability of carbon isotopes like?

A

C12 and C13- stable
C14- radioactive and unstable

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5
Q

Why are isotopes imporant?

A

Carbon dating
Trace food sources through a food web
Tracking pollution through an environment

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6
Q

What is used to measure isotopes?

A

elemental analyser-

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7
Q

What is it difficult to do with isotopes?

A

measure absolute amounts of stable isotopes so a standard will be used

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8
Q

What are some examples of standards?

A

Vienna Standard Mean Ocean Water
Pee Dee Belemnite
Canyon Diablo Troillite

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9
Q

How does using standards help measure isotopes?

A

If there are more “heavy” carbons,
the δ value will be more positive i.e.
“Heavier”
or
fewer heavy carbon will be lighter

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10
Q

What does fractionation do?

A

changes relative proportions of heavy and light isotopes.
Usually prefers lighter isotope in reactions

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11
Q

What are the 2 types of fracitonation?

A

Kinetic
Equilibrium

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12
Q

What is kinetic fractionation?

A

heavier isotope less mobile

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13
Q

What is equilibrium fractionation?

A

heavier isotope has higher binding energy

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14
Q

How can oxygen istopes be an example of fractionation?

A

Less energy needed to evaporate O16 so they enter atmo more readily when reach land and precipitate heavier O18 fall more readily

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15
Q
A
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