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Chapter 2 THE ATOMS AND MOLECULES OF ANCIENT

Chapter 2 THE ATOMS AND MOLECULES OF ANCIENT - Chapter 2...

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Chapter 2 Water and Carbon: The Chemical Basis of Life THE CHEMICAL EVOLUTION HYPOTHESIS
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Ancient Earth A mass of dust and gas particles began to collide and join together. The heat of the collisions caused a molten mass. As collisions became less frequent, the mass cooled and water vapor condensed into rain.
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Ancient Earth Rain formed the oceans around portions of the forming crust. Volcanoes released molten rock and gases from the core. The atmosphere consisted of atoms and simple molecules like H 2 O, CO 2 , CH 4 , etc.
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Elements and Atoms There are a finite number of elements on Earth. Elements are collections of atoms. Each element is unique, composed of atoms all with the same characteristics. Atoms are the basic unit of matter – living and nonliving.
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Atoms Structure – subatomic particles Nucleus: Protons Neutrons “Electron cloud”
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Atoms Atom facts: Mass number = total mass of the protons + neutrons. *Each proton and neutron has a mass of 1 AMU or 1 Dalton. (Electron mass = 1/1836 D) Atomic number = number of protons. In a stable atom with the number of electrons = the number of protons, so the atomic number also = number of electrons.
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Periodic Table Element Key 36 Kr Krypton 83.4
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Atoms Atoms Facts: All of the atoms in a certain element have the same atomic number = same number of protons. All elements have more than one form = isotopes .
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Atoms Atom Facts: Some isotopes are happy, some unhappy. Unhappy isotopes are unstable and tend to break up emitting a particle or radiation = radioactive decay .
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Atoms Atom Facts: Isotopes Radioactive decay is measured as half-life or the time it takes for ½ of the atoms in a sample to decay. One use of half-life of isotopes is determining the age of Earth and fossils – radiometric dating .
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Dating the Earth, etc. Age of the Earth ~ 4.5 billion yrs Age of the oceans ~ 4.3 billion yrs. Age of the oldest sedimentary rock ~ 3.9 billion years
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How did Earth give rise to living things? Ancient Earth consisted of atoms and simple molecules but, even the simplest living organism is composed of many different complex molecules.
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