NUCLEAR INSTABILITY

Question 1

what are the four reasons nucleis will be unstable

Answer 1

• too many protons
• too many neutrons
• too many nucleons
• too much energy

Question 2

what emmision do neutron rich nuclei under go

Answer 2

beta minus emission
n > p

Question 3

what emissions do proton rich nuclei undergo

Answer 3

beta plus and electron capture
p > n

Question 4

what emissions do nuclei with too many nucleons undergo

Answer 4

alpha decay

Question 5

what is the imbalance of stability of a nucleus

Answer 5

• nucleus is bound together by SNF
• more protons causes more electrostatic repulsion
• more neutrons are needed to balance this
• neutrons dont repel, they add to SNF

Question 6

what is meant by a metastable nucleus

Answer 6

• nucleus that exists in a particularly stable excited state

Question 7

on an N - Z graph which direction is arrow of beta minus

Answer 7

south - east

N - 1
Z + 1

Question 8

on an N - Z graph what direction is beta plus and electron capture

Answer 8

north - west

N+1
Z-1

Question 9

on an N - Z graph what direction is alpha decay

Answer 9

south - west

N - 2
Z - 2

Question 10

for a beta minus energy diagram how can we determine
1. max KE
2. number of lambdas possible
3. longest lambda

Answer 10

1. Eoriginal - Elargest energy gap
2. count the possible outcomes
3. shortest energy gap

Question 11

in closest approach how do we calculate the radius

Answer 11

Ek = Electric potential energy

r = Qq / 4pieoEk

Question 12

what are advantages of closest approach

Answer 12

1. gives a good estimate to upper limit of radius
2. alpha particles are only scatted by protons

Question 13

what are disadvantages of closest approach

Answer 13

1. will always be an overestimate, measures seperation not radius
2. alpha particles contain hadrons which are affected by SNF

Question 14

what is electron scattering

Answer 14

• use the wavelength of an electron to determine the radius of a nucleus by measuring the first minimum intensity angle

sin theta = 1.22 lambda / d

Question 15

advantages of electron scattering

Answer 15

1. electrons are leptons not affected by SNF
2. much more accurate than closest approach

Question 16

disadvantages of electron scattering

Answer 16

1. electrons must be accelerated to high speeds, because significant diffraction occurs when lambda is gap size
2. electrons can be scattered by neutrons difficult to determine intensity

Question 17

whats the nuclear radius equation

Answer 17

R = RoA^1/3

Question 18

how can we plot the radius equation

Answer 18

ln R = ln Ro + 1/3lnA

Question 19

how can we derive nuclear density

Answer 19

v = 4/3pir^3 ( assuming spherical nucleus )

v = 4/3pi (RoA^1/3 ) ^3 = 4/3piRo^3A

p = m / v so m = pv

Au / 4/3piRo^3A = 3u / 4piRo^3