Nuclear Physics

Question 1

What is the average diameter of a nucleus?

Answer 1

10¹⁵(minus)m

Question 2

What are isotopes?

Answer 2

Nuclei of the same element, that has the same proton number but different number of neutrons (nucleons number).

Question 3

What are isorons?

Answer 3

Nuclei of the same element that have the same number of neutrons but different number of protons.

Question 4

What are isobars?

Answer 4

Nuclei of the same element, that have same mass number but different number of protons.

Question 5

Law of mass-energy conservation.

Answer 5

The total amount of mass and energy together in a system is constant.

Question 6

What is mass defect?

Answer 6

Mass defect of a nucleus is equal to the difference between the total mass of the individual, separate nucleons and the mass of the nucleus.

Question 7

Define atomic mass unit (u).

Answer 7

1u is defined as ¹/₁₂ of the mass of a neutral atom of carbon-12.

Question 8

Conversion of u to kg.

Answer 8

1u = 1.6605 ×10²⁷(minus)kg

Question 9

Excess mass.

Answer 9

Mass (in u) - nucleon number.

Question 10

What is binding energy?

Answer 10

This is the minimum energy needed to pull a nucleus apart into it’s separate nucleons.

Question 11

Why are heavy elements at risk of instability?

Answer 11

This is due to their large nucleus diameter. (So nuclear force is weaker making it more unstable, as it decreases with distance)

Question 12

Range for an unstable nucleus.

Answer 12

Atomic number greater than 82.

Question 13

What is nuclear force?

Answer 13

It is a short ranged force, that provide an attractive force stronger than any repulsive electric force. shorter than inter-atom distance and are much stronger than electrostatic forces

Question 14

Define fission.

Answer 14

This is the process in which a massive nucleus splits to form two smaller fragments.

Question 15

Define Fusion.

Answer 15

The process by which two very light nuclei join together to form a heavier nucleus.(occurs in sun)

Question 16

Why is decay spontaneous?

Answer 16

• Decay of a particular nucleus isn’t affected by the presence of other nuclei.
• Decay cannot be affected by external factors such as temp and pressure. Or even chemical reactions.

Question 17

Why is decay random?

Answer 17

• Ot is impossible to predict when a particular nucleus in a sample is going to decay.
• Each nucleus in a sample has the same chance of decaying.

Question 18

What is decay constant (λ)?

Answer 18

The probability that an individual nucleus will decay per unit time interval.

Question 19

What is the activity of a radioactive sample?

Answer 19

This is the rate at which nuclei decay or disintegrate. (A = -λN) or (A= N/t) (1Bq = 1s¹(minus))

Question 20

Define half life.

Answer 20

Time taken for half the active nuclei in a sample to decay.

Question 21

To find the number N that remain Undecayed over time.

Answer 21

N = N₀exp(-λt)

Question 22

Relationships between decay constant and half life.

Answer 22

λ = 0.603/t