p6.1

Question 1

whats inside the nucleus of an atom

Answer 1

protons and neutrons these are subatomic particles

Question 2

why do the same atoms have different nuclei masses

Answer 2

because there is a difference in nuetrons

Question 3

how is heavy water created

Answer 3

by adding a neutron to a hydrogen atom

Question 4

what does it mean to be a ‘stable’ atom

Answer 4

it won’t break down or decay

Question 5

what happens to an unstable atom

Answer 5

they emit radiation, this can be a wave or particles. when an object is made up of unstable atoms it is radioactive

Question 6

whats the radiation no one cares about

Answer 6

neutron radiation, it emits neutrons

Question 7

what are the three types of radiation and what do they emit

Answer 7

radiation l type l what does it emit l
alpha l particle l helium nucleus
beta l particle l a single electron
gamma l wave l a wave on the electromagnetic spectrum

Question 8

how can you detect radiation

Answer 8

Geigur counter. this device clicks when there is radiation present, this is because the radioactive particle within the gas chamber causes a tiny electrical current

Question 9

what is penetrating power, how does it differ with the different types of radiation.

Answer 9

penetrating power is shown by what materials the radiation can pass though

• alpha stopped by skin or paper
• beta can pass through paper but is stopped by aluminium
• gamma only stopped by lead but some may still get through

Question 10

what is ionising radiation

Answer 10

radiation removes electrons from surrounding atoms and turns them into positively charged ions

Question 11

how is ionising radiation linked to penetration power

Answer 11

the higher the ionising radiation the lower the penetrating power.
alpha has a high ionising power so cant travel far
gamma doesn’t ionise at all travels the farthest

Question 12

what happens in alpha decay

Answer 12

atoms with large unstable nuclei have many protons and neutrons. two neutrons can join with two protons. this is then emitted. you can write the equation the same way you would a chemical equation. mass and charge is conserved

Question 13

what happens in beta decay

Answer 13

a neutron decays into a proton and electron. this electron is emitted. the mass of the atom does not change. a neutron and electron is lost it gains a proton

Question 14

what happens in gamma decay

Answer 14

the unstable element does not actually change in mass. but the unstable atom releases high frequency electromagnetic waves

Question 15

what happens in neutron emission

Answer 15

this is when a neutron is lost. it occurs in helium - 5 (the five represents the mass number).
it loses one neutron and becomes more stable

Question 16

how do you measure the activity of a radioactive substance

Answer 16

number of particles emitted a second is called activity / count rate. and it is measured in becquerels (Bq)

Question 17

what is half life

Answer 17

this is the time it takes for half of the object to decay.

Question 18

how are electron arranged in an atom

Answer 18

scientists worked out that atoms occupy different energy levels around the nucleus. electrons attempt to occupy the lowest energy level closest to the nucleus

Question 19

what are photons

Answer 19

they are little packets of energy, the energy of a photon is proportional to its frequency

Question 20

what does it mean to ‘excite’ an electron, why does it happen

Answer 20

this is when the electron has enough energy to jump up to the next energy level (shell). this happens when the atom absorbs the right frequency of photons

Question 21

why do atoms only absorb specific frequencies

Answer 21

because a specific amount of energy is required to cause an electron to move to one shell to another. the energy required depends on the distance between the shells.

Question 22

what is the absorption spectrum

Answer 22

these are the frequencies of light that are absorbed by the atom and electrons this is what causes electrons to become ‘excited’

Question 23

what is the emission spectrum

Answer 23

this is the frequency that the atoms emit to stop the electrons being excited.

Question 24

how are the emission spectrum and absorption spectrum related

Answer 24

the frequencies absorbed are the same as the frequencies emitted.

Question 25

whats the difference between an excited atom and an ionised atom

Answer 25

excited - the electrons have changed energy levels

ionised - the electrons have completely left the atom