9.5 Disintegration Processes

Question 1

What is an isotope?

Answer 1

form of an element with the same atomic/proton number but a different mass/nucleon number , due to different number of neutrons in nucleus

Question 2

Do the chemical properties of isotope differ from the original element? Why

Answer 2

No, because the number of protons and electrons are conserved

Question 3

Do the physical properties of an isotope differ from original element?

Answer 3

Yes, due to the different number of neutrons the density is different due to change in mass.

Question 4

What must decay equations balance?

Answer 4

Charge(atomic number), nucleon number, energy and momentum (as well as lepton,baryon,strangeness number if applicable)

Question 5

Do decay equations have to conserve mass? What is this process called?

Answer 5

No, this is a process of mass deficit

Question 6

What is an alpha particle the same as?

Answer 6

A helium nucleus.

Question 7

What does an alpha particle consist of?

Answer 7

2 protons and 2 neutrons

Question 8

What element is a typical emitter of alpha radiation?

Answer 8

americium-241

Question 9

What is the decay process of americium-241 ?

Answer 9

Am ——> Np + He

Question 10

Where does alpha radiation usually happens?

Answer 10

In very heavy atoms, due to high mass it cannot be stable

Question 11

What is the daughter element after a alpha particle is released in decay.

Answer 11

The original element’s mass number minus 4 units of mass/nucleon number. And original elements atomic number minus 2 units.

Question 12

How can we represent graphically the decay process?

Answer 12

Mass number on y axis against atomic number on x axis. The original element is plotted and daughter element too, arrow goes pointing from original to daughter ..

Question 13

What is the B- particle the same as?

Answer 13

an electron

Question 14

What is a typical emitter of B- ionising radiation?

Answer 14

strontium-90

Question 15

Example of stronium-90 decay process?

Answer 15

Sr——–> Y + B- + (anti)Ve

Question 16

Why is there a electron antineutrino in the release of B- particle?

Answer 16

Since the lepton number then becomes plus 1 on the RHS compared to 0 on LHS. Hence we need to cancel the +1 without affecting the charge as it is already 0. So we add an electron antineutrino, which has no charge and lepton number of -1.

Question 17

What happens when an element decays and releases B- radiation?

Answer 17

a neutron changes into a proton, electron and a electron antineutrino.

Question 18

What happens during B- emission in terms of atomic and mass numbers?

Answer 18

The original element’s atomic/proton number receive 1 proton and mass/nucleon number stays constant.

Question 19

When does B- emission usually happen?

Answer 19

In isotopes that are neutron rich (have many more neutrons than protons) when they decay.

Question 20

Are isolated neutrons stable?

Answer 20

No they will decay

Question 21

Why are B- particles released at random Ek, ranging from 0 to max.

Answer 21

Since during the decay process which causes the emission of B- particles, we also have 2 other particles (proton and electron antineutrino). This means that although they share momentum equally due to difference in mass they have very different energy. The neutrino thus takes the most energy.

Question 22

What does the graph look like? Intensity of B- against Ek?

Answer 22

At 0 Ek the intensity is about 3/4 of y-axis, then it increases with Ek. Then starts to drop again until intensity is 0.

Question 23

What is a B+ particle the same as?

Answer 23

A positron (anti electron)

Question 24

Typical B+ emitter?

Answer 24

Potassium-38

Question 25

what is the decay of potassium 38?

Answer 25

K —> a + B+ + Ve

Question 26

Why is there an electron neutrino produced during the decay of potassium?

Answer 26

Since B+ is essentially a positron the lepton number on RHS is -1. To make it zero while keeping charge the same we need to add an electron neutrino (lepton number of 1)

Question 27

What happns when B+ is emitted during decay?

Answer 27

proton is changed into a neutron releasing a positron and electron neutrino ,
this is seen by having the atomic number decrease by one and mass numbe stay the same

Question 28

So during the B+ emission what happens to mass/nucleon number of original element to decay into a daughter element?

Answer 28

mass/nucleon number is not changed

atomic/proton number is decreased by 1

Question 29

When is gamma radiation usually released?

Answer 29

When a nucleus is left with a surplus of energy, said to be in an excited state. This often happens after the emission of a B+ or B- or Alpha particle

Question 30

What happens to an excited nucleus?

Answer 30

Excess energy is released in form of gamma radiation to achieve a stable state.

Question 31

What can the release of B- or B+ or Alpha be accompanied by?

Answer 31

The release of gamma radiation

Question 32

How is gamma radiation similar to X Ray radiation?

Answer 32

They are both produced by excitations and have the same properties. Gamma by nucleus excitation and x rays by excited electrons

Question 33

Is there any change to element constituents when gamma radiation is emitted?

Answer 33

No, nucleus just loses energy.

Question 34

During decay how is energy split ? in terms of new nuclues, and emitted particle?

Answer 34

Nucleus takes little energy to recoil(due to great mass), most energy is taken by other particles or gamma radiation.