Atomic Structure And Radioactivity Flashcards by Enoch Akinwunmi-taylor

Plum Pudding Model

-Made by JJ Thomson in 1897
-A sphere of positive charge with negatively charged electrons dotted around inside of it

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Rutherford’s Nuclear Model

-Most of the mass is in the middle of the atom
-positively charged nucleus with a cloud of electrons around it

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Rutherford-Bohr Model of the atom

-Positive nucleus in the Centre with negatively charged electrons orbiting around the nucleus in shells
-The current model that we use

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Typical diameter of an atom

1x10(-10)m

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Typical diameter of a nucleus

1x10(-14)m

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Atomic number

-Number of protons in a nucleus
-Symbol is a curly Z
-Atoms of the same element have the same number of protons

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Mass number

-The amount of protons and neutrons in an atom
-Symbol is A

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Isotopes

Atoms of the same element with different numbers of neutrons

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Relative mass of proton

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Relative mass of neutron

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Relative mass of electron

1/2000

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Relative charge of proton

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Relative charge of neutron

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Relative charge of electron

-1

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Ion

An atoms that has gained or lost electrons so it has a charge

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Radioactive decay

-The disintegration of a nucleus
-When an unstable nucleus emits ionizing radiation to become stable
-It is random

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Radioactive materials

Materials which emit nuclear radiation

Formula for energy

-Energy= Planck’s constant x frequency
-E= hf

What are the three types of nuclear radiation?

-Alpha particles
-Beta particles
-Gamma rays

Alpha particles

-Symbol is Greek A
-Is a helium nucleus(2 protons, 2 neutrons)
-Relative charge= +2
-Strong ionizing effect
-Not very penetrating
-Stopped by sheet of paper, skin, 5cm of air

Beta particles

-An electron
-Relative charge is -1
-Weak ionizing effect
-Penetrating
-Stopped by few mm of metal

What are Gamma rays

List 6

-An electromagnetic wave
-Relative charge is 0
-Very weak ionizing effect
-Very penetrating
-Never completely stopped
-Thick concrete will reduce intensity

How do atoms move between energy layers

Giving out energy and losing photon = Go down

Taking in energy and absorbing photon = Go up

Background radiation

A measure of the amount of ionizing radiation present in an environment at a particular location that is not there because of the deliberate introduction of radioactive sources

Background radiation (Examples)

Natural - Rocks, Cosmic rays from space Man-made - The fallout from nuclear weapons testing, nuclear accidents

What is a danger of radioactivity?

-It can damage living tissue and cause DNA mutations -Cancer

Irradiation

-Exposure to ionizing radiation -Can be limited -Can be done purposefully for medical reasons

Contamination

-Being in direct contact with ionizing radiation -Are exposed for a long time (so chance for long term danger)

Activity

-The number of nuclei which decay per second -Measured in Becquerels(Bq)

Count-rate

The number of decays per second detected by a detector

Half-life

-The average time it takes for half the radioactive nuclei in a sample to decay

External radiation (Medical)

-Uses gamma rays -Multiple sources of radiation at weak power around tumour

Internal radiation (Medical)

-Uses alpha radiation -One source of radiation that is implanted into the middle of the tumor/cancerous cells

Why are gamma rays used for external radiation (medical)

-Very penetrating so can go through the skin -Not very ionizing so doesn’t hurt other bodily cells

Why are alpha particles used for internal radiation? (Medical)

-Not very penetrating -Short range so can’t ionize many bodily cells, if any -Can be easily stopped

Medical tracers

Using radioactive isotopes to leave a radioactive trail in the body and determine if an organ is healthy or not

Medical tracers (How to use it)

1. Tracer just emit radiation that can pass out of body and be detected (gamma or beta) 2. Must not be strongly ionizing, so little damage to body tissue 3. Must not decay into another radioactive isotope 4. Must have a short half-life so that it is not in the body for long

Nuclear fission

When a neutron causes a nucleus to split into 2 smaller nuclei, energy and 2 or 3 neutrons

Nuclear fusion

-The joining of 2 lighter nuclei to form a heavier nucleus -Mass may be converted into energy in the process

Energy

Energy = mass x speed of light2 E=mc2