Stable and unstable nuclei

Question 1

1 fm =

Answer 1

10^-15 m

Question 2

Range of strong nuclear force and electrostatic force.

Answer 2

• Strong force has a range of 3-4 fm.
• The electrostatic force has an infinite range but the strength decreases as the range increases.

Question 3

How does strong force affect the nucleons?

Answer 3

It has the same effect effect between any two nucleons.

Question 4

Strong nuclear force attraction and repulsion.

Answer 4

Its attractive from 3-4 to .5 fm. Below .5 fm strong force is repulsive. If it wasn’t the nucleons would be crushed into one point.

Question 5

What happens to an atom during alpha decay.

Answer 5

An alpha particle is emitted and the nucleon number decrease by 4 and the proton number decrease by 2.

Question 6

What is beta radiation?

Answer 6

A fast moving electron. The symbol for an electron as a beta particle is ⁰_-1β or β- because its charge is equal and opposite to that of a proton and its mass is much less than a proton.

Question 7

When does positron emission take place?

Answer 7

Positron emission takes place when a proton changes into a neutron in an unstable nucleus with too many protons.

Question 8

Gamma Radiation

Answer 8

Gamma radiation is electromagnetic radiation emitted by an unstable nucleus. It can pass through thick metal plates. It has no mass and no charge. It is emitted by a nucleus with too much energy, following an alpha or beta emission.

Question 9

What happens in β- emission?

Answer 9

• A neutron in the nucleus is turned into a proton.
• This causes emission of a β- particle and an antineutrino (v̅e).
• Since a neutron turns into a proton the mass no. stays the same while the atomic number decreases by 1 and changes the element.

Question 10

How were antineutrinos detected?

Answer 10

Antineutrinos were detected as a result of interactions with cadmiun nuclei in a large tank of water. This was installed next to a nuclear reactor as a controllable source of these very elusive particles. Now we know that billions of these elusive particles from the Sun sweep through our bodies every second without interacting.

Question 11

Pauli’s Hypothesis

Answer 11

In 1930, Wolfgang Pauli suggested that there was a particle that carried away the missing energy. This particle needed to be neutral and have a mass of almost zero. This hypothesis was proven 25 years later.