NMR

Question 1

nuclear spin (I)

Answer 1

The nuclei of many atoms have a property called nuclear spin (I)
Nuclear spin is really a purely quantum phenomenum

Question 2

angular momentum

Answer 2

Any spinning object has angular momentum.
In classical physics a body can have any value of angular momentum.
This isn’t true at the atomic level.

Question 3

Nuclear spin is quantised

Answer 3

• The spin of subatomic particles (nuclei, electrons…) can only have certain fixed values.
• We can think of this as ‘only particular rotation speeds are possible’.
• We say that the angular momentum is quantised. This is the basis of all of quantum theory used to describe motion at the atomic level.

Question 4

quantum number, I

Answer 4

The spin is characterised by a quantum number, I

Question 5

Even mass nuclei composed of even numbers of protons and neutrons have ____ spin

Answer 5

Even mass nuclei composed of even numbers of protons and neutrons have zero spin ( I = 0 ). So 12C, 16O have ZERO spin.

Question 6

Nuclei with even number of protons and odd number of neutrons have ____ spin

Answer 6

Nuclei with even number of protons and odd number of neutrons have 1/2 integer spin

Question 7

Nuclei with odd numbers of protons and neutrons have ______ spin values.

Answer 7

Nuclei with odd numbers of protons and neutrons have integer spin values.

Question 8

Nuclear spin is associated with

Answer 8

a magnetic field.

Question 9

If I >0 then

Answer 9

the spinning nucleus generates a magnetic field

Question 10

The resulting spin-magnet of I >0 has a

Answer 10

magnetic moment (μ) proportional to the spin.

Question 11

If we put a bar magnet in a magnetic field

Answer 11

it will align with the field

Question 12

If we put a spinning magnet in a magnetic field

Answer 12

will line up at an angle and rotate around the field direction