Absolute Age HALFLIFE AND RADIOMETRIC DATING HalfLife Atoms
Absolute Age HALF-LIFE AND RADIOMETRIC DATING
Half-Life Atoms are the building blocks of all matter.
Half-Life Atoms have 3 small parts: ◦ protons (positive charge) ◦ neutrons (no charge) ◦ electrons (negative charge)
Half-Life An element is defined by how many protons it has (this is its atomic number). Carbon’s atomic number is 6. It has 6 protons.
Half-Life Isotope: atoms of an element that have the same number of protons, but a different number of neutrons.
Half-Life Normal carbon is called carbon-12 and it has 6 neutrons. Carbon isotopes: ◦ carbon-13 has 7 neutrons ◦ carbon-14 has 8 neutrons
Atoms and Isotopes
Half-Life Isotopes can be stable or unstable. When they are unstable, they are called radioactive, and they can’t keep themselves together – they decay. Radioactive Decay
Half-Life Radioactive decay happens when an unstable nucleus changes into another kind of nucleus by releasing particles and energy.
Half-Life The isotope that decays is called the parent isotope. The stable element that forms is called the daughter isotope. Parent Daughter
Half-Life Radioactive decay is a natural clock that scientists can use to find the ages of rocks.
Half-Life Parent isotopes decay into daughter isotopes at a constant rate (the decay rate).
Half-Life The half-life of an element is the length of time it takes for half of the parent isotope to decay.
Half-Life
Half-Life The half-life of Carbon-14 is 5730 years.
Half-Life Half-life of the carbon-14 isotope: 1/1 at start 1/2 left after 5730 years 1/4 left after another 5730 years 1/8 left after another 5730 years
Half-Life
Half-Life ◦Comparing the amount of parent to daughter material determines the number of halflives the material has been through.
The Age of Earth The oldest rocks on Earth are estimated to be 4. 0 to 4. 4 billion years old.
The Age of Earth The ages of meteorites recently collected in Antarctica are 4. 5 - 4. 6 billion years old.
The Age of Earth The ages of rocks collected from the moon are about 4. 6 billion years old.
The Age of Earth is approximately 4. 6 billion years old.
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