chapter2 - Lifes Chemical Basis Chapter 2 Impacts, Issues:...

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Life’s Chemical Basis Chapter 2
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Impacts, Issues: What Are You Worth? Fifty-eight elements make up the human body
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1.1 Start With Atoms The behavior of elements, which make up all living things, starts with the structure of individual atoms
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Characteristics of Atoms Atoms are the building blocks of all substances Made up of electrons, protons and neutrons Electrons (e - ) have a negative charge Move around the nucleus Charge is an electrical property Attracts or repels other subatomic particles
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Characteristics of Atoms The nucleus contains protons and neutrons Protons (p + ) have a positive charge Neutrons have no charge Atoms differ in number of subatomic particles Atomic number (number of protons) determines the element Elements consist only of atoms with the same atomic number
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Characteristics of Atoms Isotopes Different forms of the same element, with different numbers of neutrons Mass number Total protons and neutrons in a nucleus Used to identify isotopes
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Atoms
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Fig. 2-2, p. 22 proton neutron electron
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The Periodic Table Periodic table of the elements An arrangement of the elements based on their atomic number and chemical properties Created by Dmitry Mendeleev
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Periodic Table of the Elements
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2.2 Putting Radioisotopes to Use Some radioactive isotopes – radioisotopes are used in research and medical applications
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Radioisotopes Henri Becquerel discovered radioisotopes of uranium in the late 1800s Radioactive decay Radioisotopes emit subatomic particles of energy when their nucleus breaks down, transforming one element into another at a constant rate Example: 14 C 14 N
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Tracers Tracer Any molecule with a detectable substance attached Examples: CO 2 tagged with 14 C used to track carbon through photosynthesis Radioactive tracers used in medical PET scans
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PET Scanning
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Fig. 2-4a, p. 23 A A patient is injected with a radioactive tracer and moved into a scanner like this one. Detectors that intercept radioactive decay of the tracer surround the body part of interest.
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Fig. 2-4b, p. 23
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Fig. 2-4b, p. 23 tumors B Radioactive decay detected by the scanner is converted into digital images of the body’s interior. Two tumors ( blue ) in and near the bowel of a cancer patient are visible in this PET scan.
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Animation: PET scan
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2.1-2.2 Key Concepts: Atoms and Elements Atoms are particles that are the building blocks of all matter; they can differ in numbers of protons, electrons, and neutrons Elements are pure substances, each consisting entirely of atoms with the same number of protons
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2.3 Why Electrons Matter Atoms acquire, share, and donate electrons Whether an atom will interact with other atoms depends on how many electrons it has
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Atoms and Energy Levels Electrons move around nuclei in orbitals Each orbital holds two electrons Each orbital corresponds to an energy level An electron can move in only if there is a vacancy vacancy no vacancy
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This note was uploaded on 04/02/2012 for the course BIO 100 taught by Professor Corbet during the Spring '12 term at Paradise Valley Community College .

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chapter2 - Lifes Chemical Basis Chapter 2 Impacts, Issues:...

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