BIOL125_Ch2 Text Notes

BIOL125_Ch2 Text Notes - BIOL 125 (Microbiology) Text Notes...

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BIOL 125 (Microbiology) Text Notes Chapter 2: The Chemistry of Biology 1. ATOMS, BONDS, AND MOLECULES: FUNDAMENTAL BUILDING BLOCKS a. Matter – tangible materials that occupy space and have mass. b. Atom – a tiny particle that cannot be subdivided into smaller substances without losing its properties. i. Atoms derive their properties from a combination of subatomic particles called protons, which are positively charged (p + ); neutrons, which have no charge (n 0 ); and electrons, which are negatively charged (e - ). 1) Protons and neutrons are found in the atom’s nucleus, which is surrounded by electrons. 2) Stability of atomic structure is largely maintained by: a) The mutual attraction of the protons and electrons. b) The exact balance of proton number and electron number, which causes the opposing charges to cancel each other out. c. Different Types of Atoms: Elements and Their Properties i. Element – a pure substance that has a characteristic atomic structure and predictable chemical behavior. d. The Major Elements of Life and Their Primary Characteristics i. The unique properties of each element result from the numbers of protons, neutrons, and electrons it contains. ii. Atomic Number – the number of protons an element has. The number of protons an element has does not vary. 1) Since the number of protons is equal to the number of normal electrons, the atomic number also tells us the number of normal electrons an element has. iii. Mass Number – the number of protons and neutrons an element has. 1) Mass Number – Atomic Number = number of neutrons an element has. iv. Isotopes – variant forms of the same element that differ in the number of neutrons, thereby having different mass numbers. These forms occur naturally in certain proportions. Example: Carbon exists at C-12, C-13, and C-14. a) Isotopes have virtually the same chemical properties, but some have an unstable nuclei that spontaneously release energy in the form of radiation. These isotopes are called radioactive isotopes . v. Atomic Mass (Weight) – the average mass numbers of all isotopic forms. vi. Electron Orbitals and Shells. 1) Orbitals – volumes of three-dimensional space in which an electron is likely to be found. File: 46fb834c1cbd9a50c99ae16b52b45534db644ab8.doc Updated 8/14/09
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Text Notes Chapter 2 Page 2 a) The nucleus is surrounded by electrons in orbitals that occur in levels called shells . 2) Electrons occupy energy shells. The lower-energy elections are closer to the nucleus and the higher-energy electrons are found in the farthest orbitals. 3) Electrons fill the orbitals and shells in pairs, starting with the shell nearest the nucleus. a) The first shell contains one orbital and a maximum of 2 electrons. b)
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BIOL125_Ch2 Text Notes - BIOL 125 (Microbiology) Text Notes...

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