Atomic structure

Question 1

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Answer 1

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Question 2

What are two common isotopes that are used in nuclear fission and why are they used instead of other elements (3)

Answer 2

• Plutonium 239
• Uranium 235
• They are used instead of other elements because they are massive and unstable so can be easily used to start a chain reaction.

Question 3

The fission process explained (5)

Answer 3

• In fission, the bonds that hold the nucleus together are
  broken and thermal energy is released.
• The remaining parts of the original nucleus form two
  daughter nuclei and some individual neutrons.

-When the individual neutrons collide with other
unstable nuclei they are likely to go through the same
process.
‘
- This can lead to a chain reaction of more
neutrons colliding with other unstable nuclei and the
process repeating.

• While producing more and more
  energy.

Question 4

What happens if the chain reaction of nuclear fission is not controlled (1)

Answer 4

• A nuclear explosion will go off

Question 5

How do nuclear reactors control this reaction (2)
Supply an example of materiel

Answer 5

They use control rods that can be made from a variety of elements such as (indium, silver, or cadmium) to absorb stray neutrons.

Question 6

Nuclei with too many or too few neutrons do exist but are unstable and will do what

Answer 6

decay by emitting radiation

Question 7

What happens to an atom as the number of protons increases what is required if the number of protons increases and why

Answer 7

more neutrons are required to keep the nucleus stable

Question 8

Alpha particle

Answer 8

two protons and two neutrons

Question 9

Alpha decay causes what to the mass number and atomic number

Answer 9

To decrease by 4 and the atomic number of the nucleus to decrease by 2

Question 10

How is a beta particle produced and what is it

Answer 10

If the nucleus has too many neutrons, a neutron will turn into a proton and emit a fast moving electron. This electron is called a beta particle. This process is known as beta radiation

Question 11

Electrons are not normally expected to be found in the nucleus but neutrons can split into a positive proton.

What happens next

Answer 11

An electron which has negative charge to balance the positive charge is then ejected at high speed and carries away a lot of energy

Question 12

Beta decay causes the atomic number of the nuclues to …

and the mass number to ..

Answer 12

atomic number increase by 1 and mass number is the same

Question 13

After emitting an alpha or beta particle, the nucleus will often still be too “hot”. How does the nucleus lose energy

Answer 13

The nucleus will cool down by emitting a more energetic electromagnetic wave called a gamma ray

Question 14

When can a neutron be emitted by radioactive decay

Answer 14

This can occur naturally, ie absorption of cosmic rays high up in the atmosphere can result in neutron emission.

Question 15

Neutron emission causes the mass number to decrease/increase/stay the same by x

atomic number to decrease/increase/stay the same by x

Answer 15

Mass number decrease by one and atomic number remain the same

Question 16

Alpha properties

Answer 16

Penetrating power: Skin/paper
Ionising power: high
Range in air: 5 cm

Question 17

Beta properties

Answer 17

Penetrating power: stopped by thin sheet of aluminum
ionising power: low
range in air: 1 meter

Question 18

Gamma properties

Answer 18

Penetrating power: 1 meter of concrete
Ionising power: very low
Range in air: 1 kilometer

Question 19

How do the Geiger Muller tube, or the G-M tube generally work

Answer 19

The radiation ionise the gas inside and resulting charged particles move across the chamber and get counted as charges rather like an ammeter

Question 20

Why does gamma not change the structure of a particle

Answer 20

It is pure energy

Question 21

Nuclear fuel in reactor

Answer 21

The uranium isotope that will split when triggered by an incoming neutron the fuel is held in rods so that the neutrons will fly out and cause nuclear fission in other rods.

Question 22

Graphite core in reactor

Answer 22

graphite slows the neutrons down so that they are more likely to be absorbed into a nearby fuel rod.

Question 23

Control rods

Answer 23

These are raised and lowered to stop neutrons from travelling between fuel rods and therefore change the speed of the chain reaction

Question 24

Coolant

Answer 24

This is heated up by the energy released from the fission reactions and used to boil water to drive turbines in the power station

Question 25

Concrete shield

Answer 25

The daughter products of the fission reaction are radioactive and can be a hazard

Question 26

Rutherford results of gold foil experiment (3)

Answer 26

• Most of the alpha particles did pass straight through the foil
• A small number of alpha particles were deflected by large angles (>4 degrees) as they passed through the foil
  -A very small number of alpha particles came straight back off the foil.

Question 27

Rutherford conclusions of why did most alpha particles go straight through

Answer 27

• The fact that most alpha particles went straight through the foil is evidence for the atom being mostly empty space

Question 28

Why did a small number of alpha particles get deflected at large angles. gold foil experiment. What conclusion does this give us about the atom

Answer 28

-A small number of alpha particles being deflected at large angles suggested that there is a concentration of positive charge in the atom - like charges repel, so that the positive alpha particles were being repelled by positive charges.

Question 29

Why did a very small number of alpha particles come straight back. What can this lead us to conclude.

Answer 29

-The very small number of alpha particles coming straight back suggested that the positive charge and mass are concentrated in a tiny volume of the nucleus. The tiny number doing this means the chance of being on that exact collision course was very small, and so the target being aimed at had to be equally tiny.

Question 30

What did in 1913 Bohr suggest about electrons

Answer 30

That electrons orbited the nucleus in different energy levels or at specific distances from the nucleus

Question 31

Why must electrons be arranged in fixed energy levels and not random

Answer 31

Since particular chemicals burn with certain-colored flames, the pattern of energy released by electrons in the chemical reaction must be the same for every single atom of that element

Question 32

What happens when atoms absorb electromagnetic radiation at the sub-atomic level

Answer 32

An electron can move from a lower energy level to a higher energy level. Now the atomic can now emit electromagnetic radiation and the electrons return back to there lower energy level

Question 33

Energy levels which are further from the nucleus are at higher/lower energy levels

Answer 33

higher

Question 34

Radius of nucleus is less than _____ of an atom

Answer 34

1/10000