Atomic Structure

Question 1

What is the radius of an atom?

Answer 1

1x10^-10 m

Question 2

Charges of the subatomic particles

Answer 2

proton= +1
neutron= 0
electron= -1

Question 3

Masses of the subatomic particles

Answer 3

proton= 1
neutron= 1
electron= 0

Question 4

What happens to electrons when something absorbs electromagnetic radiation?

Answer 4

the electrons are moved to a higher energy level, further from the nucleus

Question 5

What happens to electrons when something emits electromagnetic radiation?

Answer 5

the electron drops to a lower energy level, closer to to the nucleus

Question 6

Positive ion

Answer 6

when an atom has LOST an electron

Question 7

Negative ion

Answer 7

when an atom has GAINED an electron

Question 8

What do all atoms of an element have the same of?

Answer 8

proton number (atomic number)

Question 9

Mass Number

Answer 9

number of protons and neutrons in a nucleus

Question 10

Atomic Number

Answer 10

Number of protons

Question 11

Isotopes

Answer 11

atoms of an element that have the same number of protons, so are from the same element, but they have a different number of neutrons

Question 12

Plum pudding model

Answer 12

the atom is a ball of positive charge with negative electrons embedded in it.

Question 13

Gold Foil Experiment: Results

Answer 13

most passed straight through
some were deflected so they must have been repelled by the same charge that the alpha particle carried
the repelling charge must have been heavier than the alpha or it would have passed straight through

Question 14

Gold Foil: Conclusions

Answer 14

mass of the atom in in a central, positively charged nucleus
the electrons surround the nucleus

Question 15

Role of Neils Bohr

Answer 15

adapted the model by suggesting that electrons orbit the nucleus at set distances

Question 16

The results of the later experiments

Answer 16

the positive charge of the nucleus can be divided into a whole number of smaller particles, each with the same amount of positive charge, commonly known as protons

Question 17

Role of James Chadwick

Answer 17

1932
carried out a number of experiments which provided evidence that in the nucleus there was also a particle called the neutron

Question 18

Which type of nuclei, decay, and why?

Answer 18

Unstable nuclei give out radiation to become more stable

Question 19

Activity

Answer 19

the rate at which something decays

Question 20

What is activity measured in?

Answer 20

Becquerels

Question 21

One Becquerel=

Answer 21

One decay per second, one count rate per second

Question 22

Count rate

Answer 22

the number of decays per second

Question 23

3 types of nuclear decay

Answer 23

alpha, beta, gamma

Question 24

Alpha

Answer 24

• 2 protons, 2 neutrons
  -strong ionising power
  -absorbed by a few cm of air/paper
  -can cause damage to living cells

Question 25

Beta

Answer 25

• high-speed electron, ejected from the nucleus which turns into a proton and electron, of which the electron is emitted
• reasonable ionising power
  -absorbed by a few mm of aluminium
  -can cause damage to cells if absorbed
  -can penetrate into organs

Question 26

Gamma

Answer 26

• Electromagnetic radiation
  -poor ionising power
  -absorbed by many cm of lead/many m of concrete
• can pass through cells without being absorbed

Question 27

Radioactive contamination

Answer 27

unwanted presence of materials containing radioactive atoms on other materials

Question 28

Irradiation

Answer 28

The process of exposing an object to nuclear radiation
Deliberate/Accidental
Does not cause the object to become radioactive

Question 29

Ways of protecting from unwanted radiation

Answer 29

use sources with the lowest activity for the shortest time
wear appropriate clothing, e.g. lead apron
no handling sources with bare hands

Question 30

Hazards of contamination

Answer 30

Food contaminated with an alpha source would be more hazardous than if it had gamma radiation
An area contaminated with alpha would not be dangerous unless it was entered, due to the low penetration of alpha radiation
However, if it was contaminated with a source of gamma radiation, this would irradiate people nearby

Question 31

Half-Life

Answer 31

-the time it takes for half the nuclei to decay
-time taken for the half-life to fall to 50%

Question 32

Alpha in the nuclear equation

Answer 32

Mass is reduced by 4
The atomic number is reduced by 2

Question 33

Beta in the nuclear equation

Answer 33

mass remains the same
the atomic number is increased by 1