Atomic Structure

Question 1

Evolution of the plum pudding model

Answer 1

Around 1900 JJ Thomspson discovered electrons. He said atoms where spheres of positive charge with tiny negative electrons stuck in them

Question 2

Alpha particle stattering experiment

Answer 2

1909 ernest Rutherford fired beams of alpha particles at a thin sheet of gold foil. A circular detector screen was placed around the gold doil and alpha particle source.

They expected that the positively charged alpha particles would go straight through or be slightly deflected

More than expected where deflected and some came back at them

Question 3

What was concluded from the scattering experiment

Answer 3

Atoms must have positively charged nuclei in the centre because most 9f the particles went through the foil so most of the atoms are empty space.
The nucleus must have a strong positive charge as some alpha particles where deflected at a large angle.

Question 4

What did Niels Bohr do

Answer 4

Adapted the nuclear model so electrons are in energy levels

Question 5

What did james Chadwick do

Answer 5

1932 proved the existence of neutrons wich explained the imbalance between atomic and mass number

Question 6

How small is the nucleus of an atom

Answer 6

10000 times smaller tha the radius if an atom

Question 7

What is the radius of an atom

Answer 7

1 x 10-10m

Question 8

What is the relative mass of an electron

Answer 8

1/2000

Question 9

What is the atomic and mass nummber

Answer 9

Atomic is nummber of protons

Mass is protons and neutrons

Question 10

What are ions and isotopes

Answer 10

Ions are charged particles with a different number of electrons
Isotopes have a different nummber of neutrons

Question 11

What is radioactive decay

Answer 11

Unstable isotopes decaying into other elements to try to become more stable

Question 12

What is ionizing radiation

Answer 12

Radiation that knocks electrons off atoms, creating positive ions

Question 13

What is alpha radiation

Answer 13

Where an alpha particles is admitted from nucleus

An alpha particle is 2 neurons and 2 protons - the same as helium.

Question 14

What happens to charge when alpha radiation is released

Answer 14

Decrease the charge and atomic nummber by 2

The mass number decreases by 4

Question 15

How ionizing is alpha radiation

Answer 15

They are big so strongly ionizing . Can be stopped by paper and only travel a few cm into the air. Slow moving

Question 16

What is beta decay

Answer 16

A fast moving electron released by a nucleus so virtually no mass.

Question 17

What happens to the charge and mass when a nucleus decays by neta decay

Answer 17

A neutron turns into a proton, releasing a b particle. This increases the charge on the nucleus and atomic nummber by one.

Question 18

How ionizing is beat radiation

Answer 18

Moderately ionizing. Move quite fast and are quite small. They are absorbed by a sheet of aluminium. Have a range of a few meters in the air

Question 19

What is gamma decay

Answer 19

Very short wavelength electromagnetic waves released by the nucleus. They have no mass or charge.

Pass straight through materials and through the air. They are weakly ionizing because they dont collide with atoms. Absorbed by thick sheets of concrete.

Question 20

What does a Geiger Miller tube do

Answer 20

Measure the amount of radiation counts reaching it per second

Question 21

What is half life

Answer 21

The time it takes for the number of nuclei of a radioactive isotope in a sample to halve

Question 22

What does the length of half life say about the the stability of the nuclei

Answer 22

The shorter the half life, the more unstable the nuclei are

Question 23

What does it mean that an object is irradiated

Answer 23

Exposed to a radioactive source

Question 24

What are some ways to reduce e the risk of radiation

Answer 24

Keeping sources in lead lines boxes
Standing behind barriers
Using remote controlled arms to handle sources

Question 25

When is an object said to be contaminated

Answer 25

When unwanted radioactive atoms get onto a material

Question 26

What is the most dangerous radiation outside the body

Answer 26

Beta and gamma as it can penetrate the body and get into organs

Question 27

What is the most dangerous radiation inside the body

Answer 27

Alpha because it does damage in a localized area

Question 28

What is radiation dose

Answer 28

A measure if the risk of harm to your body due to exposure to radiation
Measured in sieverts (Sv)

Question 29

What is backround radiation

Answer 29

Low level radiation that is present at all times
It come from naturally occurring unstable isotopes, cosmetic Ray’s from space (mostly from the sun) and radiation due to man made sources eg nuclear weapon tests and dumped nuclear waste

Question 30

How does location affect the radiation you ar exposed to

Answer 30

Certain underground rocks can cause higher levels of radiation at the surface. A radon dector can tell you if it’s in your home and a radon outlet pipe can be used to keep levels down.
People who live at higher altitudes get more cosmic Ray’s

Question 31

What occupations expose you to more radiation

Answer 31

Nuclear industry workers
Radiographers
Undergroudees

Question 32

How is ionizing radiation dangerous to cells

Answer 32

Enters cells and collides with molecules wich causes ionization wich damages and destroys molecules

Question 33

How does radiation cause cancer

Answer 33

Lower dosage causes damage to cells.this gives rise to mutant cells wich divide uncontrollably forming a tumour

Higher dosage kills cells completely wich causes radiatin sickness

Question 34

How can radioactive isotopes be used in medicine

Answer 34

Injected and their progress around the body can be followed using an external detector. All isotopes used must be gamma or beta emitters so radiation passes out of the body

Radiotherapy for cancer where gamma Ray’s are used. Has to be used at the right dosage so it doesn’t kill normal cells.radiactive implants can also be put next to tumors

Question 35

What is nuclear fission

Answer 35

A type of nuclear reaction used to release energy from large unstable atoms by spitting them into smaller ones

Question 36

What does the nucleus have to do before it will split

Answer 36

Absorbe a neutron

Question 37

What are the elements like that are formed after an atom spilts

Answer 37

There are 2 of them. They are lighter and roughly the same size and have the same energy in their kenetic stores

2 or 3 neurons are also released. If one of these is moving slowly enough to be absorbed by another nucleus or can cause another fission to happen.

Question 38

What reaction 8s used to generate nuclear energy

Answer 38

Nuclear fission

Question 39

What happens to the energy of the products of nuclear fission

Answer 39

The energy unit transferred to the products are carried away by gamma rays and kenetic stors of remaining free neutrons

Question 40

How is the amount of energy released in a fission reaction controlled

Answer 40

Control rods wich are lowered and raised inside nuclear reactors to absorb neutons wich slows down the chain reaction

Question 41

What is nuclear fusion

Answer 41

Nuclei collide at high speed and fuse together to create a larger heavier nucleus.

Question 42

What are the properties of the products of nuclear fusion

Answer 42

The heavier nucleus doesn’t have as much mass as the separate nuclei. Some of the mass is converted into energy rich is released as radiation

Question 43

Why dont we used fusion to generate electricity

Answer 43

The temperatures and pressures needed are too high so fusion reactors are hard and expensive to build