Atom Structure And Nuclear Radiation

Question 1

What is the radius of an atom?

Answer 1

About 1 × 10⁻¹⁰ metres.

Question 2

What is the structure of an atom?

Answer 2

A small, dense, positively charged nucleus containing protons and neutrons, surrounded by negatively charged electrons in energy levels.

Question 3

What is the radius of a nucleus compared to the whole atom?

Answer 3

Less than 1/10,000 of the atom’s radius.

Question 4

What happens when an atom absorbs electromagnetic radiation?

Answer 4

Electrons move to a higher energy level.

Question 5

What happens when an atom emits electromagnetic radiation?

Answer 5

Electrons move to a lower energy level.

Question 6

What is the atomic number of an atom?

Answer 6

The number of protons in the nucleus.

Question 7

What is the mass number of an atom?

Answer 7

The total number of protons and neutrons.

Question 8

What is an isotope?

Answer 8

Atoms of the same element with the same number of protons but different numbers of neutrons.

Question 9

What is radioactive decay?

Answer 9

The random process where unstable atomic nuclei release radiation to become more stable.

Question 10

Name the four types of nuclear radiation.

Answer 10

Alpha particles, beta particles, gamma rays, and neutrons.

Question 11

What is an alpha particle?

Answer 11

Two protons and two neutrons — the same as a helium nucleus.

Question 12

What is a beta particle?

Answer 12

A high-speed electron emitted when a neutron turns into a proton.

Question 13

What is a gamma ray?

Answer 13

High-energy electromagnetic radiation emitted from the nucleus.

Question 14

What is the range of alpha particles in air?

Answer 14

A few centimeters.

Question 15

What is the range of beta particles in air?

Answer 15

A few metres.

Question 16

What is the range of gamma rays in air?

Answer 16

Many kilometres.

Question 17

What stops alpha radiation?

Answer 17

A sheet of paper or skin.

Question 18

What stops beta radiation?

Answer 18

A few millimetres of aluminium.

Question 19

What stops gamma radiation?

Answer 19

Several centimetres of lead or metres of concrete.

Question 20

Which type of radiation has the greatest ionising power?

Answer 20

Alpha particles.

Question 21

Which type of radiation has the least ionising power?

Answer 21

Gamma rays.

Question 22

What is activity?

Answer 22

The rate at which a radioactive source decays, measured in becquerels (Bq).

Question 23

What is count-rate?

Answer 23

The number of decays detected per second by a detector like a Geiger-Muller tube.

Question 24

Write the symbol for an alpha particle in a nuclear equation.

Answer 24

\text{ } ^4_2\text{He} \text{ or } \alpha \text{ }

Question 25

Write the symbol for a beta particle in a nuclear equation.

Answer 25

\text{ } ^0_{-1}\text{e} \text{ or } \beta \text{ }

Question 26

What happens to mass and charge during alpha decay?

Answer 26

Mass number decreases by 4, atomic number decreases by 2.

Question 27

What happens to mass and charge during beta decay?

Answer 27

Mass number stays the same, atomic number increases by 1.

Question 28

What happens to mass and charge during gamma emission?

Answer 28

No change to mass number or atomic number.

Question 29

What is meant by half-life?

Answer 29

The time it takes for half of the radioactive nuclei in a sample to decay.

Question 30

How can you calculate net decline after a number of half-lives?

Answer 30

Net decline = 1 ÷ (2ⁿ), where n is the number of half-lives.

Question 31

What is radioactive contamination?

Answer 31

When radioactive material is deposited on surfaces or inside objects.

Question 32

What is irradiation?

Answer 32

Exposure to radiation without becoming radioactive.

Question 33

How can hazards of irradiation and contamination be reduced?

Answer 33

Use shielding, handle sources remotely, limit exposure time.

Question 34

Why is peer review important in radiation studies?

Answer 34

To ensure findings are valid, reliable, and safe before practical use.

Question 35

What are sources of background radiation?

Answer 35

Natural (rocks, radon gas, cosmic rays) and artificial (nuclear fallout, medical use).

Question 36

What affects a person’s radiation dose?

Answer 36

Occupation and location.

Question 37

How is radiation dose measured?

Answer 37

In sieverts (Sv).

Question 38

Why do hazards of radioactive materials depend on half-life?

Answer 38

Short half-life = high activity but brief danger; long half-life = low activity but long-term risk.

Question 39

What are medical uses of nuclear radiation?

Answer 39

Exploring internal organs (tracers) and controlling/destroying cancerous tissue (radiotherapy).

Question 40

What is nuclear fission?

Answer 40

Splitting a large nucleus into smaller nuclei, releasing energy and neutrons.

Question 41

What triggers nuclear fission?

Answer 41

Absorption of a neutron.

Question 42

What is a chain reaction in nuclear fission?

Answer 42

Released neutrons cause more nuclei to undergo fission.

Question 43

How is a chain reaction controlled in a nuclear reactor?

Answer 43

By absorbing some neutrons using control rods.

Question 44

What is nuclear fusion?

Answer 44

Joining of two light nuclei to form a heavier nucleus, releasing energy.

Question 45

Why is nuclear fusion hard to achieve?

Answer 45

Requires very high temperatures and pressures to overcome electrostatic repulsion.