Atomic Structure 3

What is radioactivity

The spontaneous emission of radiation by unstable nuclei

What is radiation

Emission of energy through space as particles or waves

Who discovered radioactivity

Henri Becquerel

What did Becquerel observe

Darkening of photographic plates by uranium salts

Who coined the term radioactivity

Marie Curie

What did Marie Curie discover

Radioactive materials more active than uranium

What are the three types of radioactive decay

Alpha beta gamma

What is an alpha particle

A helium nucleus with 2 protons and 2 neutrons

Charge of alpha particle

+2

Mass of alpha particle

4

What is a beta particle

A high speed electron emitted from nucleus

Charge of beta particle

-1

Mass of beta particle

1/1840

What is gamma radiation

High frequency electromagnetic radiation

Charge of gamma radiation

0

Mass of gamma radiation

0

Which is most ionizing

Alpha

Which is least ionizing

Gamma

Which is most penetrating

Gamma

Which is least penetrating

Alpha

What stops alpha radiation

Paper or skin

What stops beta radiation

Aluminium sheet

What stops gamma radiation

Lead or thick concrete

Why is alpha highly ionizing

High charge and mass

Why is gamma least ionizing

No charge and no mass

Speed of gamma radiation

Speed of light

Relative speed beta vs alpha

Beta faster than alpha

Which particle is slowest

Alpha

What happens in beta decay

A neutron converts to proton and electron

What happens in alpha decay

Nucleus emits helium nucleus

What happens in gamma emission

Energy released from excited nucleus

What is positron

A particle like electron but positive charge

What is positron decay

Proton converts to neutron and positron

What is electron capture

Nucleus captures inner electron forming neutron

When does electron capture occur

When insufficient energy for positron emission

What is nuclear equation

Equation showing radioactive decay

What must balance in nuclear equation

Mass number and atomic number

What does alpha decay do to mass number

Decreases by 4

What does alpha decay do to atomic number

Decreases by 2

What does beta decay do to atomic number

Increases by 1

What does beta decay do to mass number

No change

What does gamma decay do

Releases energy only

What is band of stability

Graph of neutrons vs protons for stable nuclei

What are stable nuclei

Atoms within band of stability

What happens outside band

Atoms undergo decay

What is neutron rich nucleus

High N/P ratio

What decay occurs for neutron rich

Beta decay

What is proton rich nucleus

Low N/P ratio

What decay occurs for proton rich

Positron decay or electron capture

What happens to heavy nuclei Z>83

Undergo alpha decay

What is carbon-14 dating

Method to determine age of fossils

Why is carbon-14 useful

It decays at constant rate

Half-life of carbon-14

5700 years

What happens to carbon-14 after death

It decays reducing ratio

What is geological dating

Using isotopes like uranium to date rocks

What isotope used in rock dating

Uranium-238

Half-life of uranium-238

4.5 billion years

What does U-238 decay into

Lead-206

How is rock age determined

Ratio of U-238 to Pb-206

What are radioisotopes

Isotopes used in applications

Use of iodine-131

Thyroid function testing

Use of sodium-24

Blood circulation tracking

Use of thallium-201

Detect heart damage

Use of technetium-99m

Locate tumors and organs

Use of cobalt-60

Cancer treatment

Use of radium-226

Cancer therapy

What are tracers

Isotopes used to track processes

Why tracers need short half-life

Reduce radiation exposure

Why dating isotopes need long half-life

Measure long time spans

What is natural radioactivity

Spontaneous nuclear reactions

What is artificial radioactivity

Induced nuclear reactions

How is artificial radioactivity produced

Bombarding atoms with particles

Which is easier to control

Artificial radioactivity

What is half-life

Time for quantity to reduce to half

Are half-lives constant

Yes

What happens after one half-life

Half remains

What happens after two half-lives

One quarter remains

What is radiation sickness

Illness from high radiation exposure

What radiation causes sickness

Beta and high energy radiation

What are acute effects

Short term illness

What are long term effects

Cancer and genetic damage

Why gamma radiation dangerous

Highly penetrating

What happens to DNA from radiation

Damage and mutations

What happens to dividing cells

More affected by radiation

Why alpha radiation low risk externally

Low penetration

Why alpha radiation dangerous internally

High ionization inside body

What is ionizing radiation

Radiation that removes electrons

What is penetrating power

Ability to pass through materials

What is stability curve

Graph predicting decay

What determines decay type

N/P ratio

Which radiation is deflected in fields

Alpha and beta

Which radiation is not deflected

Gamma

Direction alpha deflection

Slight deflection

Direction beta deflection

Greater deflection opposite direction

Why beta deflects more

Lower mass

What happens to excited nucleus

Emits gamma radiation

What is nuclear transmutation

Change of one element to another