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Year 9 Chemical Reactions- Nuclear Decay and Carbon Dating

Radiation, Nuclear decay, half-life, carbon dating
by

Cassandra Comyns

on 25 October 2014

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Transcript of Year 9 Chemical Reactions- Nuclear Decay and Carbon Dating

Year 9 Science; Chemical Reactions
Radioactivity...

Quick Quiz! 1-6 in your workbook...
Review: What do we know about
the atom???
What particles are located
in the NUCLEUS?
Question 1...
What particles are located in
the area AROUND the nucleus?
Question 2...
What is the charge of a:
PROTON?
Question 3...
5
4
Neutron?
Electron?
Question 6...
What is the difference between
the ATOMIC number and MASS
number?
Answers
1. Proton & neutron
2. Electron
3. Positive
4. Neutral
5. Negative
6. The ATOMIC NUMBER is the number of the
protons in the nucleus whereas the MASS
number is the number of the protons PLUS
the neutrons
The Electromagnetic Spectrum
Identified by 3 pieces of
information:
1. Chemical Symbol (X)
2. Atomic number (Z)
3. Atomic Mass (A)
Remember
Classifying
Atoms:

... An 'element' is all atoms that have the same number of PROTONS... this is how we classify them as one element.
What is it that tells us how many protons an element has?
Remember... Elements...
Nuclear Decay
Some nuclei eject particles at high speeds. This is NUCLEAR DECAY
During nuclear decay, atoms may change from one atom to another. This is TRANSMUTATION
"Transmute"
Transmute (or "transmutation") is a class of sub-skills of [Alchemy]. It is highly valued since it allows the transmutation of some metals into more valuable ones, and transmutation of some elemental items into harder to find ones.
-World of Warcraft WIKI (WOWWIKI)
Type 1; alpha decay
There are 3 types of nuclear decay...
Type 2; beta decay
Type 3; gamma decay
Nucleus ejects an
alpha particle
Alpha particle: cluster of 2 protons and 2 neutrons (identical to a helium-4 nucleus!)
When the nucleus carries many neutrons, one neutron may break down into a PROTON and an ELECTRON
The nucleus ejects a beta particle (identical to electrons- very small, with a negative charge)
Occurs when the nucleus is very high in energy
The nucleus will emit a gamma ray
It is ENERGY that is released, not a PARTICLE.
Applications of Radioactive Decay
Half-life
Carbon dating
Half-life
The rate at which nuclear decay takes place is measured by a radioisotopes half-life
How does this knowledge help scientists?
Carbon Dating
•The half-life of carbon-14 is used to determine the age of fossil and ancient materials through a process known as carbon dating.
Proteins
Fats & lipids
Carbohydrates
We have carbon throughout our whole body...
•C-14 is radioactive
•When the organism is alive, C-14 is constantly replenished.
How Carbon dating works...
Electromagnetic radiation is a type of energy released OR absorbed by charged particles- it exhibits wave-like behaviour as it travels through space...
The
electromagnetic spectrum
is the range of all possible types of radiation

The nucleus of an atom (protons + neutrons) is constantly moving, vibrating, pulsating, rotating, and rearranging.
This movement causes some nuclei to emit
electromagnetic radiation
.
Remember...
Not all atoms of an element have
the same number of neutrons!
Most of the atoms that make up matter contain stable nuclei & never undergo nuclear decay...
Example: Carbon-12 and Carbon-13
Some
atoms have unstable nuclei & could eject particles/electromagnetic waves from their nucleus at any moment & undergo nuclear decay.
Example: Pu-240 changes into Uranium (U-236)
(This is because the number of protons has changed!)
Example: C-14 changes into N-14 with a beta particle emitted
Some nuclei eject particles at high speed- this is known as a
nuclear reaction
, or
nuclear decay
.
ISOTOPES...
These unstable atoms are
radioisotopes
.
Carbon-14 is an example of a radioisotope.
After the gamma ray is emitted, the nucleus returns to a lower energy state
Gamma rays are a form of electromagnetic waves (Refer to electromagnetic spectrum)
These are very powerful waves, and can have harmful effects
The half-life of a radioisotope is the time it takes for half the nuclei to decay
(Varies from a fraction of a second to millions of years)
•When the organism dies, C-14 in the body begins to decay into N-14.
• Scientists can measure the amount of C-14 in fossils and bones, and estimate when the animal lived/died
Only occurs in atoms with very heavy nuclei (usually when mass number is greater than 100)
One element will turn into another... (TRANSMUTATION)
The atomic number increases by one
The mass number does not change, as the total number of protons and neutrons stays the same
Relies on the fact that all living things contain a small amount of C-14
Full transcript