• Stable and Unstable Nuclei

Question 1

How do we know that there is a force holding together stable isotopes?

Answer 1

• A stable isotope has nuclei that do not disintegrate, therefore there must be a force holding them together that overcomes the electrostatic forces of repulsion between protons, and holds protons and neutrons together

Question 2

What force holds stable nuclei together?

Answer 2

Strong nuclear force.

Question 3

What are some key features of the strong nuclear force?

Answer 3

• It has a very small range, of 4 fm.
• Has the same effect between two protons as it does between two neutrons or a proton and a neutron.
• It is an attractive force from 3-4fm, to 0.5fm, smaller than this and it becomes a repulsive force in order to prevent neutrons and protons from being pushed into each other.

Question 4

What are the three types of radiation released by radioactive isotopes?

Answer 4

• Alpha
• Beta
• Gamma

Question 5

What is a key difference between strong nuclear force and electrostatic force in terms of range?

Answer 5

• Strong nuclear force has a range of 3-4 fm,

* Electrostatic repulsive force has an infinite range, although the force gets weaker as the distance is increased.

Question 6

What does alpha radiation consist of?

Answer 6

Alpha particles

Question 7

What is the composition of alpha particles?

Answer 7

• 2 Protons
• 2 Neutrons
• 4 Mass Number

Question 8

Where does alpha emission occur?

Answer 8

Alpha emission only occurs in very big nuclei, that are unstable.

Question 9

Why does alpha emission occur?

Answer 9

Nuclei are too large for the strong nuclear force to keep them stable.

Question 10

What happens to an element when an alpha particle is emitted?

Answer 10

• Proton Number decreases by two.

* Nucleon number decreases by four.

Question 11

What is the range of alpha particles?

Answer 11

Very short.

They only a reach a few cm in air.

Question 12

What does beta radiation consist of?

Answer 12

• Consists of fast moving electrons.

* An uncharged anti-neutrino.

Question 13

How does the charge & mass of a beta particle compare to that of a proton?

Answer 13

• Charge is equal and opposite to the charge of a proton.

* Mass is much smaller than the mass of a proton.

Question 14

Where does beta decay occur?

Answer 14

• Beta decay occurs in isotopes that are unstable due to being neutron rich ( having too many more more neutrons than protons in the nucleus ).

Question 15

What happens in the process of the emission of a beta particle?

Answer 15

• A neutron in the nucleus changes into a proton.
• Beta particle is created when the change occurs, and is instantly emitted.
• An anti neutrino is emitted ( anti particle with no charge ).

Question 16

What happens to the element during the beta emission?

Answer 16

• A neutron changes into a proton in the nucleus.
• Atom number increases by 1, however the nucleon number remains the same.
• Due to a change in proton number, the the product nucleus is now a part of a different element.

Question 17

Why is the anti neutrino released in beta emission?

Answer 17

It carries away some energy and momentum, in order to follow the conservation of energy.

Question 18

What is gamma radiation?

Answer 18

• Gamma radiation is electromagnetic radiation emitted by an unstable nucleus.

Question 19

What are some features of gamma radiation?

Answer 19

• it can pass through thick metal plates.

* Has no charge and no mass.

Question 20

When is gamma radiation emitted?

Answer 20

• Emitted by a nucleus with too much energy, following an alpha or beta emission.