P4

Question 1

What’s the radius of an atom?

Answer 1

1 × 10-10 meters.

Question 2

What’s the basic structure of an atom?

Answer 2

Positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons.

Question 3

How big is the nucleus in comparison to an atom?

Answer 3

The radius of a nucleus is less than 1/10 000 of the radius of an atom.

Question 4

Where in an atom is the most concentrated?

Answer 4

Most of the mass of an atom is concentrated in the nucleus.

Question 5

What are different energy levels?

Answer 5

The electrons are arranged at different distances from the nucleus.

Question 6

In an atom which 2 subatomic particles have the same number of particles?

Answer 6

Electrons and protons.

Question 7

What is the atomic number?

Answer 7

Number of protons.

Question 8

What is the mass number?

Answer 8

Number of protons and neutrons

Question 9

What is an isotope?

Answer 9

Atoms of the same element that have different numbers of neutrons

Question 10

Does the atom became positive or negative charged if it loses an electron?

Answer 10

Positive charged.

Question 11

Why might a scientific model be changed or replaced?

Answer 11

New experimental evidence.

Question 12

Before the discovery of the electron, what were atoms thought to be?

Answer 12

Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided.

Question 13

What led to the plum pudding model of the atom?

Answer 13

The discovery of the atom.

Question 14

What does the plum pudding model look like?

Answer 14

Sea of positive charge with negative electrons inside.

Question 15

What knowledge did the alpha particle scattering experiment come out with?

Answer 15

Mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. This nuclear model replaced the plum pudding model.

Question 16

How was the nuclear model changed and by who?

Answer 16

Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances.

Question 17

Who decided neutrons existed?

Answer 17

Chadwick.

Question 18

What was the order in which subatomic particles were discovered?

Answer 18

1. Electrons. 2. Protons. 3. Neutrons.

Question 19

What is radioactive decay?

Answer 19

Some atomic nuclei are unstable. The nucleus gives out radiation as it changes to become more stable.

Question 20

What is activity and what is it measured in?

Answer 20

Activity is the rate at which a source of unstable nuclei decays. Activity is measured in becquerel (Bq)

Question 21

What is count - rate?

Answer 21

Count-rate is the number of decays recorded each second by a detector (eg Geiger-Muller tube).

Question 22

What are the 4 things that can be emitted from a nucleus?

Answer 22

1. Alpha particle. 2. Beta particle. 3. Gamma ray. 4. Neutron.

Question 23

What is an alpha particle?

Answer 23

Consists of 2 protons and 2 neutrons (helium nucleus).

Question 24

What is a beta particle?

Answer 24

A high speed electron ejected from the nucleus as a neutron turns into a proton

Question 25

What is a gamma ray?

Answer 25

Electromagnetic radiation from the nucleus

Question 26

What is an alpha particle's penetration power and ionising power like?

Answer 26

It cannot penetrate through materials and is stopped quickly. Paper absorbs it. It's highly ionising.

Question 27

What is an beta particle's penetration power and ionising power like?

Answer 27

They are absorbed by aluminium. Moderately ionising.

Question 28

What is a gamma ray's penetration power and ionising power like?

Answer 28

Travel far without being stopped and only absorbed by thick lead or concrete. As it passes through things and not collide with atoms; it is weakly ionising.

Question 29

What's an alpha particle equation?

Answer 29

4 / 2 He

Question 30

What's a beta particle equation?

Answer 30

0 / -1 e

Question 31

What happens with the numbers with gamma rays?

Answer 31

The emission of a gamma ray does not cause the mass or the charge of the nucleus to change.

Question 32

Is radioactive decay random?

Answer 32

Yes

Question 33

What is the half - life?

Answer 33

The half-life of a radioactive isotope is the time it takes for the number of nuclei of the isotope in a sample to halve, or the time it takes for the count rate (or activity) from a sample containing the isotope to fall to half its initial level.

Question 34

What is radioactive contamination?

Answer 34

Radioactive contamination is the unwanted presence of materials containing radioactive atoms on other materials.

Question 35

Compare the hazards associated with contamination and irradiation.

Answer 35

High levels of contamination of alpha is the most dangerous they can harm in one localised area. Gamma is the least dangerous as it's weakly ionising so can pass through the body. High levels of irradiation from all sources are dangerous especially beta and gamma as they can penetrate the skin and get to your vital organs.

Question 36

How to protect yourself from irradiation?

Answer 36

Gloves and tongs. Protective suits.

Question 37

How is peer review going to protect us?

Answer 37

The more we understand means the more we can protect ourselves. Once peer reviews; info can be accepted and improvements can be made.

Question 38

Where can background radiation come from? (2)

Answer 38

1. Natural sources such as rocks and cosmic rays from space. 2. Man-made sources such as the fallout from nuclear weapons testing and nuclear accidents.

Question 39

What is radiation dose measured in?

Answer 39

Radiation dose is measured in sieverts (Sv)

Question 40

Gamma rays can kill what and why?

Answer 40

Cancer - high doses of it can kill the cells.

Question 41

Nuclear radiations are used in medicine for the: (2)

Answer 41

1. exploration of internal organs. 2. control or destruction of unwanted tissue

Question 42

Radiation can do what?

Answer 42

Enter living cells and ionise them. This leads to tissue damage.

Question 43

What is nuclear fission?

Answer 43

Nuclear fission is the splitting of a large and unstable nucleus (eg uranium or plutonium).

Question 44

What happens in nuclear fission?

Answer 44

1. Usually, for fission to occur the unstable nucleus must first absorb a neutron. 2. The nucleus undergoing fission splits into two smaller nuclei, roughly equal in size, and emits two or three neutrons plus gamma rays. 3. Energy is released by the fission reaction. 4. All of the fission products have kinetic energy. 5. The neutrons may go on to start a chain reaction. 6. The chain reaction is controlled in a nuclear reactor to control the energy released.

Question 45

What causes a nuclear explosion?

Answer 45

An uncontrolled chain reaction.

Question 46

What is nuclear fusion?

Answer 46

Nuclear fusion is the joining of two light nuclei to form a heavier nucleus. In this process some of the mass may be converted into the energy of radiation.