Isotopes and standards

Question 1

What is an isotope?

Answer 1

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

Question 2

What is the proportion of different carbon isotopes?

Answer 2

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

Question 3

What is the ratio of C13/C12?

Answer 3

0.011

Question 4

What is the stability of carbon isotopes like?

Answer 4

C12 and C13- stable
C14- radioactive and unstable

Question 5

Why are isotopes imporant?

Answer 5

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

Question 6

What is used to measure isotopes?

Answer 6

elemental analyser-

Question 7

What is it difficult to do with isotopes?

Answer 7

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

Question 8

What are some examples of standards?

Answer 8

Vienna Standard Mean Ocean Water
Pee Dee Belemnite
Canyon Diablo Troillite

Question 9

How does using standards help measure isotopes?

Answer 9

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

Question 10

What does fractionation do?

Answer 10

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

Question 11

What are the 2 types of fracitonation?

Answer 11

Kinetic
Equilibrium

Question 12

What is kinetic fractionation?

Answer 12

heavier isotope less mobile

Question 13

What is equilibrium fractionation?

Answer 13

heavier isotope has higher binding energy

Question 14

How can oxygen istopes be an example of fractionation?

Answer 14

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