Radioactivity

Radioactivity (explanation)

Certain isotopes of elements have an unstable nucleus. The nucleus gives off energy to make itself stable it breaks up, shoots small pieces of itself off, and giving off energy

Radioactivity (definition)

The spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation

History of radioactivity

Henri Bequerel discovered radioactivity. Pierre and Marie Curie were the first to discover radioactive elements (Polonium and Radium)

Alpha particles symbol

a

Alpha particles (explanation)

Consists of 2 protons + 2 neutrons (no electrons). Same as helium nucleus and is shown as 4 He 2 or He+2, due to no electrons. Heavy and slow

What do you need to remember when it comes to alpha particle calculations

Atomic mass number of parent element decreases by 4. Atomic number of parent element decreases by 2. Move back 2 on periodic table.

Draw the symbol for Beta particles in sketchbook

β

Beta particle (properties)

A singular electron, light and fast. shown as 0e-1

Beta particle/emission explanation

Neutron from nucleus turns into a proton + electron. Electron is shot off

What do you need to remember about Beta particles/emission calculations?

Mass number doesn't change. Move forward one space on the Periodic Table.

Radioactivity calculations (notes)

When selecting a symbol for the element, base it off atomic number and not atomic mass number due to isotopes

Gamma Radiation (explanation)

strong form of electromagnetic radiation. Travels at the speed of light. Dangerous due to high energy and speed. No changes to number of protons or electrons

Draw the symbol for gamma rays in sketchbook

γ

Note for penetration

lighter the radiation = more penetration/dangerous

Draw an alpha particle in the sketchbook app

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Charge (Alpha particle)

positive

Penetrating power (Alpha particle)

Weak (stopped by paper)

Example/Use (Alpha particle)

Americium-241. Used in smoke detectors

Charge (Beta Particle)

negative

Draw a Beta particle in sketchbook

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Penetrating power (Beta Particle)

Medium (Stopped by 4mm of aluminium)

Example/Use (Beta Particle)

Carbon-14. Used for radiocarbon/carbon-14 dating

Draw gamma ray in sketchbook

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Charge (Gamma Ray)

None

Penetrating power (Gamma Ray)

Strong. (Stopped by several cms of lead)

Example/Use (Gamma Ray)

Cobalt-60. Used in cancer treatment

Features of Chemical Reactions

Involves electrons, No new element formed, No release of nuclear radiation. Bonds broken + formed.

Features of Nuclear Reactions

Involves nucleus. New elements formed. Release of nuclear radiation. No bonds broken + formed

Nuclear Reaction (definition)

A process that alters the composition, structure or energy of an atomic nucleus

Half-life (definition)

The time taken for half the nuclei of a radioactive sample to decay.

Half-life (explanation)

Half of the sample decays after one half life. Half of what remains (1/4 of the original sample) remains after two half lives etc.

Half-life (Example)

Half-life of Carbon-14 is 5730 years. If we start with 10g of Carbon-14, after 5730 years half the sample will have decayed to nitrogen leaving 5g of Carbon-14. After another 5730 years half of that will have decayed leaving 2.5g of Carbon-14

Radiocarbon/Carbon-14 Dating (definition)

A technique used to find the age of an object containing carbon. It is based on the ratio of Carbon-14: Carbon-12 in the object

What is a radioisotope?

Isotope with unstable nucleus

Half-life of a radioisotope (definition)

Time taken for half of the sample to decay.

One risk associated with exposure to alpha radiation

Causes cancer

Why are people who live in a house with americium-241 smoke detectors not at risk from alpha radiation?

Alpha radiation is not very penetrating

Does the americium-241 in a smoke detector need to be replaced often?

No, as it’s half-life is very long