10 Atoms and radioactivity

Question 1

What is an atom made of and what is its structure?

Answer 1

Protons and neutrons in a central nucleus, orbiting electrons

Question 2

What are the charged particles particles in an atom?

Answer 2

Protons have positive (+) charge, electrons have equal negative (-) charge

Question 3

How much more massive are protons and neutrons compared to electrons?

Answer 3

About 1800 times more massive than an electron

Question 4

What forces hold an atom together?

Answer 4

Electrons held in orbit by attraction between opposite charges, protons and neutrons held tightly together by strong nuclear force

Question 5

What is the smallest “piece” of an element you can have?

Answer 5

An atom

Question 6

What is the atomic number (proton number) of an element?

Answer 6

Number of protons in the atoms of an element

Question 7

What are isotopes, and what are the similarities and differences between them?

Answer 7

Different versions of the same element, same number of protons, different numbers of neutrons; same atomic number, different mass numbers

Question 8

What is the mass number (nucleon number)?

Answer 8

The total number of protons and neutrons in the nucleus

Question 9

How many electrons can be held in the first and second shells of an atom?

Answer 9

First shell - 2, second shell - 8

Question 10

What are the elements and their chemical symbols of atomic numbers 1, 2, 3, 4, 5, 6, 7, 8, 88, 90, 92, 94

Answer 10

Hydrogen (H) - 1, Helium (He) - 2, Lithium (Li) - 3, Beryllium (Be) - 4, Boron (B) - 5, Carbon (C) - 6, Nitrogen (N) - 7, Oxygen (O) - 8, Radium (Ra) - 88, Thorium (Th) - 90, Uranium (U) - 92, Plutonium (Pu) - 94

Question 11

What is the periodic table?

Answer 11

A chart of all the elements, sorted into groups

Question 12

What causes nuclear radiation to be emitted, and how?

Answer 12

Some materials contain atoms with unstable nuclei, which disintegrate in time (radioactive decay); as this happens, tiny particles and sometimes waves are emitted called nuclear radiation. Materials which emit these are called radioactive

Question 13

What, specifically, is radioactive?

Answer 13

Particular isotopes of an element are radioactive

Question 14

What are some isotopes of elements with stable and unstable nuclei and where are they found?

Answer 14

Carbon-12 & carbon-13 are stable; carbon-14 is unstable; found in air, plants, animals. Potassium-39 is stable; potassium-40 is unstable; found in rocks, plants, sea water. Uranium-234 is unstable and found in rocks. Uranium-235 and 238 are both unstable

Question 15

What are the 3 main types of nuclear radiation?

Answer 15

Alpha particles, beta particles, gamma rays

Question 16

What is the structure of the 3 main types of nuclear radiation?

Answer 16

Alpha particles - 2 protons and 2 neutrons (identical to helium-4 nucleus); beta particles - an electron; gamma rays - electromagnetic waves similar to X-rays

Question 17

What are ions and how are they formed?

Answer 17

Charged atoms (or groups of atoms). Formed when atoms lose or gain electrons

Question 18

What types of radiation are ionising and why?

Answer 18

Nuclear radiation can remove electrons from atoms in path, so ionising; ultraviolet and X-rays also ionising radiation

Question 19

What is the relative charge and mass of the 3 main types of nuclear radiation?

Answer 19

Alpha particles (+2 relative charge with high mass compared to betas); beta particles (-1 relative charge with low mass); gamma rays (0 relative charge and no mass)

Question 20

What are the speeds of the 3 main types of nuclear radiation?

Answer 20

Alpha particles (up to 0.1 * light speed); beta particles (up to 0.9 * light speed); gamma rays (light speed)

Question 21

What are the ionising and penetrating effects of the 3 main types of radiation?

Answer 21

Alpha particles (strongly ionising, not very penetrating. Stopped by skin, thick paper sheet or few cm of air); beta particles (weakly ionising, penetrating but stopped by few mm of aluminium); gamma rays (very weakly ionising, very penetrating, never completely stopped though intensity reduced by lead and thick concrete)

Question 22

How are the 3 main types of nuclear radiation affected by magnetic and electric fields?

Answer 22

Alpha particles (deflected), beta particles (deflected), gamma rays (not deflected)

Question 23

What are the dangers of nuclear radiation?

Answer 23

Can damage or destroy living cells and stop organs working properly, can cause mutations in cells, which may then grow abnormally and cause cancer

Question 24

How does risk from nuclear radiation vary with exposure and type?

Answer 24

Greater the intensity and exposure time of radiation, greater risk; radioactive gas and dust taken in body especially dangerous, alpha radiation most harmful; less risk from sources outside body, beta and gamma rays potentially most harmful due to penetration into internal organs

Question 25

Why are alpha particles more ionising than beta particles and gamma rays?

Answer 25

Alpha particles have greater charge, more force on electrons, and slower, greater time close to electrons. Gamma rays uncharged so least ionising

Question 26

What is background radiation and what are its sources?

Answer 26

Radiation around all the time due to radioactive materials in environment; mainly from natural sources like soil, rocks, air, building materials, food, drink, space; in some areas over half comes from radioactive gas (radon-222) seeping out of rocks

Question 27

What is a Geiger–Müller tube and how does it work?

Answer 27

Used to detect alpha, beta and gamma radiation. Window at end thin enough for alpha particles to enter, they ionise gas inside, sets off high-voltage spark across gas and pulse of current in circuit. Beta particles or gamma radiation burst same effect

Question 28

What can a Geiger–Müller (GM) tube be connected to and what do they do?

Answer 28

A ratemeter - gives reading in counts per second; a scaler - counts total number of particles (or bursts of gamma radiation) detected by tube; an amplifier and loudspeaker - loudspeaker makes "click" when radiation detected

Question 29

What is included when the radiation from a radioactive source is measured?

Answer 29

Reading always includes any background radiation present, reading for background radiation alone must be found and subtracted from total

Question 30

What is a cloud chamber?