CHAPTER2 - Chapter 2: Essential Chemistry for Biology I....

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Chapter 2: Essential Chemistry for Biology I. Matter A. Anything that occupies space and has mass B. Composed of elements which are made up of atoms II. Subatomic particles A. Protons 1. Positively charged 2. Found in the nucleus of the atom B. Neutrons 1. No electrical charge 2. Also found in the nucleus C. Electrons 1. Negative electrical charge 2. Found outside the nucleus in energy levels or orbitals III. Atoms A. Each atom has a specific number of protons in the nucleus = atomic number B. The total number of protons and neutrons in the nucleus of an atom = mass number C. In a typical atom, the number of protons equals the number of electrons = overall charge of the atom is neutral D. Example: a neutral atom of sodium has an atomic number of 11 and a mass number of 23 1. Number of protons -__11______ 2. Number of neutrons -___12____ 3. Number of electrons - ___11____ E. The number of electrons at each energy level is fairly specific 1. The energy level closest to the nucleus - can hold a maximum of 2 electrons 2. The second level - can hold a maximum of 8 electrons 3. The third level and beyond - can hold a maximum of 18 electrons, but prefer 8 electrons 4. The electrons in the outermost level are referred to as valence electrons and are involved in chemical bonding F. Isotopes 1. Different forms of an atom that have the same atomic number, but different mass numbers 2. The number of neutrons is different 3. Example - carbon normally has 6 protons and 6 neutrons a. One isotope of carbon has 6 protons and 7 neutrons b. A second isotope of carbon has 6 protons and 8 neutrons 4. Significance of isotopes: a. Used in medical diagnosis - radioactive isotopes b. Used by archeologists to age and study fossils
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Chapter 2 page 2 IV. Elements A. Substances that cannot be broken down into simpler substances by a chemical reaction b. Traditionally recognized that there are 92 natural and 17 synthetic c. 98% of an organisms mass is composed of 6 elements: 1. Carbon (C) 2. Hydrogen (H) 3. Oxygen (O)
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CHAPTER2 - Chapter 2: Essential Chemistry for Biology I....

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