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Question 1

who came up with the plum pudding model?

Answer 1

• JJ Thompson

Question 2

describe the plum pudding model

Answer 2

• an atom with a ball of positive charge surrounded by electrons (which carry a negative charge)

Question 3

which two scientists conducted the alpha-scattering experiment?

Answer 3

• Marsden and Rutherford

Question 4

describe the alpha-scattering experiment

Answer 4

1. Scientists took a piece of gold foil
2. Scientists then fired POSITIVE alpha particles at the gold
   - Most of the alpha particles passed straight through = so most of the atom is EMPTY SPACE.
   - Sometimes, the alpha particles bounce straight back = the centre of the atom contains the MOST MASS.
   - Some deflected slightly = the CENTRE OF THE ATOM HAS A POSITIVE CHARGE.

Question 5

what did Bohr discover?

Answer 5

• electrons orbit the nucleus

Question 6

what did James Chadwick discover?

Answer 6

• the nucleus contains neutrons

Question 7

in which order were protons, neutrons and electrons discovered?

Answer 7

• electrons, protons and neutrons

Question 8

• describe the nuclear model of the atom

Answer 8

• The model has a very small positively charged nucleus surrounded by outer electrons at a large distance from the nucleus. The protons and neutrons, which contain nearly all of the mass of the atom, are located in the nucleus at the centre of the atom.

Question 9

what is the radius of an atom?

Answer 9

• 1 x 10^-10 m

Question 10

what is the radius of a nucleus?

Answer 10

• 1 x 10^-14 m

Question 11

what kind of process is radioactive decay?

Answer 11

• random

Question 12

what are the units of radioactivity?

Answer 12

• Becquerels (Bq)

Question 13

what piece of equipment is used to measure radioactive decay?

Answer 13

gieger counter

Question 14

what is an alpha particle?

Answer 14

• helium nucleus (2 protons and 2 neutrons)

Question 15

what is the range of an alpha particle in the air?

Answer 15

• a few cm

Question 16

what are beta particles?

Answer 16

• fast-moving electrons (e-1)

Question 17

what is the range of a beta particle in the air?

Answer 17

• a few metres

Question 18

what are gamma rays?

Answer 18

• an electromagnetic wave

Question 19

what is the range of a gamma ray in the air?

Answer 19

• several metres

Question 20

what can an alpha particle be stopped by?

Answer 20

• stopped by a sheet of paper

Question 21

what can a beta particle be stopped by?

Answer 21

• stopped by a thin sheet of aluminium

Question 22

what can a gamma ray be stopped by?

Answer 22

• concrete or a thick block of lead

Question 23

what is the ionising power of an alpha particle?

Answer 23

• very strong

Question 24

what is the ionising power of a beta particle?

Answer 24

• quite strong

Question 25

what is the ionising power of a gamma ray?

Answer 25

- weak

Question 26

what is meant by the term a half-life?

Answer 26

- the amount of time it takes for a nuclei to divide

Question 27

what is irradiation?

Answer 27

- the process by which an object is exposed to radiation.

Question 28

what is ionising radiation?

Answer 28

- the radiation emitted from unstable nuclei

Question 29

what precautions should people take when working with radioactive isotopes?

Answer 29

- wear a lead apron - use a lead glass screen - use a radiation monitor to see how much radiation a person receives

Question 30

what is radioactive contamination?

Answer 30

- when unwanted radioactive isotopes end up on other materials.

Question 31

what is the nuclear equation of a beta particle?

Answer 31

- mass number does not change - atomic number increases by 1

Question 32

what is the nuclear equation of an alpha particle?

Answer 32

- mass number decreases by 4 - atomic number decreases by 2

Question 33

what is the nuclear equation of a gamma ray?

Answer 33

- the mass and atomic number do not change in gamma radiation