Atomic Sructure- Paper 1

Question 1

What is the current model of the atom?
Electrons moving energy levels?

Answer 1

.nucleus=mass of the atom. protons (+1 relative charge) and neutrons (which are neutral,0)=positive charge.
.rest of the atom is mostly empty space.
.Negative electrons (relative charge -I)
.The number of protons = the number of electrons

.Electrons in energy levels can move within atom. gain energy absorbing EM radiation move to a higher energy level, further from the nucleus.
-release EM radiation move to a lower energy level that is closer to the nucleus.
-outer electrons leaves the atom, the atom becomes a positively charged ion.

Question 2

What are Isotopes?

Answer 2

1)All atoms of each element have a set number of protons-atomic number.
2) The mass number of an atom (the mass of the nucleus) number of protons + the number of neutrons in its nucleus.
3) Isotopes of an element are atoms with the same number of protons but a different number of neutrons

Question 3

What is radioactive decay?
Process of radioactive decay?

Answer 3

1)unstable isotopes decay into other elements=radiation more stable.

2) Radioactive substances spit out one or more types of ionising radiation from nucleus
3)They can also release neutrons (n) when they decay, rebalance their atomic and mass numbers.

Question 4

What is ionising radiation?

Answer 4

radiation that knocks electrons off atoms, creating positive ions. The ionising power of a radiation source is how easily it can do this.

Question 5

What radiation is used in smoke detectors and how?

Answer 5

Alpha radiation=ionises air particles, causing a current to flow. smoke in the air, it binds to the ions - meaning the current stops=alarm sounds.

Question 6

Alpha Particles? 4 and 1

Answer 6

1) two neutrons and two protons (helium nucleus).
-don’t penetrate very far into materials
- only travel few cm in air
-absorbed by sheet of paper.
-strongly ionising.

Question 7

Beta Particles? 5 + 1

Answer 7

1) neutron in the nucleus turns into a proton= fast-moving electron released
-virtually no mass and a charge of -1.
-moderately ionising.
-penetrate moderately far into materials
-colliding, a range in air of a few metres.
-absorbed by a sheet of aluminium

Question 8

Gamma Rays? 4 +1

Answer 8

1)Gamma raus (y) are waves of electromagnetic radiation released by the nucleus.
-penetrate far into materials without being stopped
-travel a long distance through air
-weakly ionising tend to pass through rather collide with atoms.
-absorbed by thick sheets of lead or metres of concrete.

Question 9

Making Radioactive equations?

Answer 9

1) They’re written in the form: atom before decay -> atom after decay + radiation emitted.
2) total mass and atomic numbers must be equal on both sides.

Question 10

Alpha Decay?

Answer 10

.atomic number reduces by 2, mass number reduces by 4. written as a helium nucleus.

Question 11

Beta Decay

Answer 11

1)mass number doesn’t change
2)atomic number add 1 due negative electron 0 -1e

Question 12

Gamma Rays? 2

Answer 12

1)Don’t Change Charge or Mass of the Nucleus (rid excess energy from nucleus.)
2)no change to the atomic mass or atomic number of the atom.

Question 13

What detector counts radiation counts?
Is radioactive decay random?
What is half life?
What is activity?

Answer 13

1)Geiger-Muller tube and counter=records the count-rate - number radiation counts per second.
2) Radioactive decay random=can’t predict
3) time it takes for the amount of radiation emitted by source to halve=half-life.
4) Half-life find the rate at which a source decays=ACTIVITY. becquerels, Bq (1 Bq is I decay per second).

Question 14

The Radioactivity of a Source Decreases Over Time? 2

Answer 14

1) radioactive nucleus decays become a stable nucleus, activity whole decrease.
2) activity never reaches zero=half-life to measure how quickly the activity drops off.

Question 15

What is a half-life?
What is a short and long half life?

Answer 15

=time taken for the number of radioactive nuclei in an isotope to halve.

-short half-life= activity falls quickly= very unstable=rapidly decay. high amount of radiation start, quickly become safe.
-long half-life= activity falls more slowly nuclei don’t decay long time=releasing small amounts of radiation=long time.
dangerous because nearby areas are exposed to radiation for (millions of) years.

Question 16

Measuring Half-Life Using a Graph?

Answer 16

1)plot a graph of activity against time will always be shaped curved.
2)half-life is found from the graph by finding the time interval bottom axis corresponding halving of the activity on vertical axis.

Question 17

Background Radiation? 3

Answer 17

.Background radiation is the low-level radiation around us all the time. always measure subtract background radiation from results
1) air, food, building materials, rocks.
2)space, cosmic rays. mostly from the Sun. Earth’s atmosphere protects us
3)human activity, e.g. nuclear explosions or nuclear waste

Question 18

Radiation dose?
What is the unit?

Answer 18

.radiation dose tells risk of harm to body tissues due to exposure to radiation.
. sieverts (Sv)
-The dose from background radiation is small,so millisieverts are often used (1 Sv = 1000 mSv).

Question 19

Irradiation?
How can you prevent this? 3

Answer 19

1)exposed to radiation.Irradiating something does not make it radioactive
2) lead-lined boxes, barriers, different room using remote-controlled arms reducing the effects.

Question 20

Contamination?
How to prevent this? 3

Answer 20

.unwanted radioactive atoms get onto or into an object.
1) contaminating atoms decay=releasing radiation harm.

3)Gloves, tongs, avoid particles getting stuck to your skin or under your nails.

Question 21

Contamination or irradiation?

Answer 21

1)Outside body=beta and gamma sources most dangerous. Beta and gamma penetrate body get to the delicate organs.
-Alpha is less dangerous because it can’t penetrate the skin blocked by a small air gap.

2)Inside body=alpha sources most dangerous, damage localised area.
Beta sources less damaging=radiation absorbed wider area=Gamma sources least dangerous pass straight out - lowest ionising power.

Question 22

Risks to Using Radiation?

Answer 22

1)Radiation enter living cells ionise atoms and molecules within them=tissue damage.
2) Lower doses tend to cause minor damage without killing the cells.=mutant cells=divide uncontrollably=cancer.
3) Higher doses tend to kill cells completely=radiation sickness (vomiting) if lot of cells all get blatted at once.

Question 23

Gamma Sources are Usually Used in? 2

Answer 23

1) Medical Tracers: injected people progress, followed using external detector.
2) Isotopes= GAMMA= radiation passes out body without causing much ionisation.short half-life radioactivity disappears.

Question 24

1)Radiotherapy?
2) what can gamma ray and beta do?

Answer 24

.high doses ionising radiation kill all living cells=treat cancers.
-Gamma rays directed carefully right dosage to kill cancer cells without damaging too many normal cells.
-Radiation-emitting implants (beta-emitters) next to or inside tumours=damage normal cells,=feel very ill.

Question 25

Risks and Benefits of using radiation to treat cancer? 2 benefits 1 risk

Answer 25

.tracers diagnose life-threatening conditions
.risk of cancer from one use tracer is small.

-prolonged exposure to radiation poses future risks, causes many side effects

Question 26

What is Nuclear Fission? 7

Answer 26

1) large unstable atoms splitting=smaller atoms nucleus=absorb a neutron before it will split.
2) splits two new lighter elements some energy
3)Two or three neutrons released atom splits. absorbed by another nucleus, more fission=chain reaction
4)free neutrons, heat water, making steam to turn turbines and generators
5)amount of energy= changing how quickly=chain reaction.
-control rods, lowered,raised inside nuclear reactor to absorb neutrons, slow down
6)Uncontrolled chain reactions=lots of energy=explosion - nuclear weapons

Question 27

Nuclear Fusion? 4

Answer 27

1) two light nuclei collide high speed=join (fuse) to larger=heavier nucleus.
2) heavier nucleus does not have much mass as two separate, light nuclei did. mass lighter nuclei=converted to energy.
3)Fusion releases a lot of energy
4)temperatures and pressures needed for fusion are so high that fusion reactors are really hard and expensive to build.

Question 28

Atomic structure: John dalton? And Democritus?

Answer 28

1)1804 John Dalton agreed Democritus matter was made up of tiny spheres that couldn’t be broken up, each element made up different types.

Question 29

Atomic structure: JJ Thomson?

Answer 29

2)I. J. Thomson discovered particles electrons that could be removed from atoms. spheres of positive charge tiny negative electrons stuck in them=plum pudding model,

Question 30

Atomic structure: Rutherford?

Answer 30

3)1909, Rutherford tried firing a beam of alpha particles thin gold foil - alpha scattering experiment. expected particles to pass straight through the gold sheet,
-few alpha particles deflected back=most mass atom must be concentrated centre tiny nucleus.
-nucleus have positive charge, repelled the positive alpha particles.
-alpha particles passed straight through, atom empty space. =nuclear model of the atom

= discovered that the positively charged nucleus of all materials could be broken down into smaller positively charged particles

Question 31

Atomic structure: Neil Bohr?

Answer 31

4)Niels Bohr electrons orbiting the nucleus do at certain distances=energy levels.

Question 32

James Chadwick?

Answer 32

6)James Chadwick proved the existence of the neutron, explained imbalance between the atomic and mass numbers.
A neutron has a mass similar to the proton
A neutron has no charge - it is neutral