4.4 Atomic structure

Question 1

What is the structure of an atom?

Answer 1

The atom has a nucleus of protons and neutrons, surrounded by electrons in shells.

Question 2

What is the relative charge of a proton?

Answer 2

1

Question 3

What is the relative charge of a neutron?

Answer 3

0

Question 4

What is the relative charge of an electron?

Answer 4

-1

Question 5

What is the relative mass of a proton?

Answer 5

1

Question 6

What is the relative mass of a neutron?

Answer 6

1

Question 7

What is the relative mass of an electron?

Answer 7

Approximately 0 (1/1836)

Question 8

What is the atomic number of an atom?

Answer 8

The number of protons in the nucleus.

Question 9

What is the mass number of an atom?

Answer 9

The total number of protons and neutrons in the nucleus.

Question 10

What are isotopes?

Answer 10

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

Question 11

Who proposed the nuclear model of the atom?

Answer 11

Ernest Rutherford.

Question 12

What did Rutherford’s alpha scattering experiment show?

Answer 12

Atoms have a dense, positive nucleus and are mostly empty space.

Question 13

How did Bohr improve the atomic model?

Answer 13

He proposed electrons orbit the nucleus at fixed energy levels.

Question 14

What is radioactive decay?

Answer 14

Spontaneous process where unstable nuclei emit radiation to become more stable.

Question 15

What are the three types of nuclear radiation?

Answer 15

Alpha (α), Beta (β), Gamma (γ).

Question 16

What is an alpha particle?

Answer 16

Two protons and two neutrons (helium nucleus).

Question 17

What is a beta particle?

Answer 17

A high-speed electron from a decaying neutron.

Question 18

What is gamma radiation?

Answer 18

High-energy electromagnetic radiation emitted from a nucleus.

Question 19

Which type of radiation is most ionising?

Answer 19

Alpha radiation.

Question 20

Which type of radiation is most penetrating?

Answer 20

Gamma radiation.

Question 21

What is half-life?

Answer 21

Time for half the radioactive nuclei in a sample to decay.

Question 22

What is activity measured in?

Answer 22

Becquerels (Bq).

Question 23

What is contamination?

Answer 23

Unwanted radioactive material on or in an object.

Question 24

What is irradiation?

Answer 24

Exposure to radiation without contact with radioactive material.

Question 25

What are the dangers of radiation?

Answer 25

Can damage or kill cells, and cause mutations or cancer.

Question 26

How can people protect from radiation?

Answer 26

Limit exposure time, increase distance, use shielding.

Question 27

What is nuclear fission?

Answer 27

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

Question 28

What is nuclear fusion?

Answer 28

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

Question 29

Where does fusion occur naturally?

Answer 29

In stars like the Sun.

Question 30

Why is fusion difficult on Earth?

Answer 30

It needs very high temperatures and pressures.

Question 31

What is the radius of an atom?

Answer 31

About 1 × 10⁻¹⁰ meters.

Question 32

How does the nucleus radius compare to the atom?

Answer 32

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

Question 33

How can electrons change energy levels?

Answer 33

By absorbing or emitting electromagnetic radiation.

Question 34

What is count-rate?

Answer 34

Number of decays detected per second.

Question 35

What is neutron emission?

Answer 35

Release of a neutron during radioactive decay.

Question 36

What are the properties of alpha radiation?

Answer 36

Low penetration, high ionising power, stopped by paper.

Question 37

What are the properties of beta radiation?

Answer 37

Moderate penetration and ionising power, stopped by aluminium.

Question 38

What are the properties of gamma radiation?

Answer 38

High penetration, low ionising power, reduced by lead.

Question 39

What are some uses of radiation?

Answer 39

Alpha: smoke detectors; Beta: thickness control; Gamma: sterilisation and cancer treatment.

Question 40

How are nuclear equations balanced?

Answer 40

By conserving atomic and mass numbers on both sides.

Question 41

What happens to atomic and mass number in alpha decay?

Answer 41

Atomic number decreases by 2, mass number by 4.

Question 42

What happens to atomic and mass number in beta decay?

Answer 42

Atomic number increases by 1, mass number stays the same.

Question 43

Why is radioactive decay random?

Answer 43

It’s impossible to predict when a specific nucleus will decay.