Atomic structure COPY

Question 1

what is the radius of an atom?

Answer 1

1 x 10^-10 metres

Question 2

when does the energy level of an electron change?`

Answer 2

when the atom emits or absorbs electromagnetic radiation

Question 3

what is the radius of a nucleus

Answer 3

1/1000 the radius of an atom

Question 4

what happens when atoms absorb electromagnetic radiation

Answer 4

electrons to a higher energy level

Question 5

what happens when atoms emit electromagnetic radiation

Answer 5

electrons drop to a lower energy level

Question 6

What is radioactive decay?

Answer 6

when isotopes are unstable and decay into other elements and give out radiation as they try to become more stable

Question 7

what does the type of radiation depend on?

Answer 7

why the nucleus is unstable and is spontaneous

Question 8

what are 4 types of nucleur radiation?

Answer 8

alpa beta gamma neutron

Question 9

What is ionising radiation?

Answer 9

radiation that creates positive ions. *the ionising power of radiation source is how easily it can do this

Question 10

What is activity?

Answer 10

the rate at which a source of unstable nuclei decays.

Question 11

what is activity measured in?

Answer 11

becquerel (Bq)

Question 12

What is the count-rate?

Answer 12

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

Question 13

What do alpha particles consist of?

Answer 13

two neutrons and two protons the same as a helium nucleus

Question 14

What is alpha radiation?

Answer 14

when an alpha particle is emitted from the nucleus

Question 15

What are the features of alpha radiation?

Answer 15

• they don’t penetrate very far into materials and are stopped quickly
• they can only travel a few cms in air and are absorbed by a sheet of paper
• because of their size they are strong ionising

Question 16

What is a beta particle?

Answer 16

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

Question 17

What are features of beta radiation?

Answer 17

• they are moderately ionising
• they penetrate moderately far into materials before colliding and have a range in air of a few metres.
• they are absorbed by a sheet of aluminium

Question 18

what is a gamma ray?

Answer 18

electromagnetic radiation from the nucleus

Question 19

What are features of gamma radiation?

Answer 19

• they penetrate far into material without being stopped and will travel a long distance through air
• they are weakly ionising because they pass through rather than collide with atoms

* eventually they hit something and do damage

• they can be absorbed bu thick sheets of lead or metres of concrete

Question 20

What happens during beta decay?

Answer 20

a neutron in the nucleus turns into a proton and releases a fast-moving electron

because the nucleus has lost a neutron and gained a proton the mass doesnt change

Question 21

Gamma rays don’t change the charge or mass of the nucleus.

What do they do instead?

Answer 21

They get rid of excess energy from a nucleus

Question 22

Radioactive decay is spontaneous, however, with a _______________ it is possible to predict how many decay in a certain time period

Answer 22

large enough number of nuclei