Define these terms Define: The law of original horizontality Index fossil Stratigraphy Petrifaction Altered remains Unconformity Angular unconformity Superposition Name the five stages in sedimentary rock formation Explain why fossils are found primarily in sedimentary? What is the cambrian explosion? What is the fundamental idea behind fossil succession?

AMU atomic mass unit Atoms have three main components. Each of these has mass. Two of them have charge. Protons and neutrons are treated as being equal in mass. This mass is 1 amu. In fact there is a slight difference. be considered to have the same mass. The mass of an electron is 5/10,000ths of an amu. The charge of a proton is +; the charge of an electron is negative. These charges are equal, but opposite.

AMU and isotopes The proton and neutron are located in the nucleus. The nucleus is approximately 1 x m in diameter. An entire atom can be from 1 – 5 x m. The volume outside of the nucleus is called the electron cloud. It is much, much larger than the nucleus. Because the mass of an electron is so small compared to the mass of the proton and neutron (5/10,000ths), it is not used to determine atomic mass. The atomic mass of an atom is calculated by adding the mass of the protons and the mass of the neutrons found in the nucleus.

AMU, isotopes and radioactivity The number of protons in an atom’s nucleus uniquely determines which element that atom is. The number of neutrons is another matter. An isotope is one of the possible variants (versions) of any given element that nature has allowed/created. The variation that makes an atom an isotope is the number of neutrons in the nucleus.

AMU, isotopes and radioactivity Radioactivity refers to the ‘spontaneous’ decay of a nucleus. It is a form of alchemy, or maybe like a nervous breakdown. The three types of radioactive decay are: Alpha,α Beta,βGamma,ϒ Alpha,α Beta,βGamma,ϒ

AMU, isotopes and radioactivity The three symbols for the three types of radioactive decay are: ϒ β α What makes the types of decay different? How would you write the symbols that show the decay sequence of Uranium?

Radioactive Decay The atoms of certain elements have ________________ nuclei that tend to break apart into more stable atoms. This breaking apart or decay is called ______________. The original atom is known as the _____________________ atom and the new atoms created by decay are known as the _________________ atoms. There are three types of radioactive decay. Each one differs in what is emitted during decay. Parent Atom Daughter Atoms Alpha decay involves the loss of a Helium atom from the nucleus. This means that the parent atom changes because proton number has been reduced.

Radioactive Decay Parent Material Half life: Amount of time in which half of the isotope will be changed into daughter material. A, Initial condition = 100% Parent Decay particles After 1 half life 50%, or ½ of the original amount is still a radioactive isotope 50% Parent 50% daughter A1A1 B1B1 50%, or ½ of the original amount is now a different molecule

Parent Material In another half life A 1 has been reduced by 50% again. The newly created daughter material is just like the the other daughter material. Condition after 1 half life: 50% Parent, 50% daughter Decay particles After 2 half lives 25%, or 1/4 of the original amount. 25% Parent A1A1 B1B1 A2A2 Parent Materi al B2B2 75% is daughter material Daughter material Daughter material New daugh ter matl

Half-Life The time that it takes for ½ of the parent material to decay into the daughter material is known as the _____________________. The half-life is a known amount of time for each element – each element has a different half-life length. For example, uranium-238 decays into lead-206 at a half-life of 4.5 billion years.

Radiocarbon Dating When an organism dies, the carbon-14 contained in the body starts to decay. The ratio of carbon-14 (parent material) to carbon-12 (daughter material) is determined. The age of the organism is known by known the carbon-14:carbon-12 ratio and the length of the half- life.