LifeisChemistry

LifeisChemistry - Life is chemistry Atoms and Molecules The...

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Unformatted text preview: Life is chemistry! Atoms and Molecules: The Chemical Basis of Life • A knowledge of chemistry is essential to understand biology!!! Atom – The smallest portion of an element that retains its chemical properties Elements – Substances that cannot be broken down into simpler substances by ordinary chemical reactions (made of atoms of the same type) – Each has a chemical symbol Molecule The smallest group of two or more atoms that retains its chemical properties •Subatomic particles include – Electron—carries a negative charge – Proton—carries a positive charge – Neutron—uncharged particle •The number of protons in the atomic nucleus ( known as the atomic number ) defines an element Characteristics of protons, neutrons, and electrons Not a very good representation!!!! A better one . . . • The number of protons in the atomic nucleus (known as the atomic number ) defines an element • Four elements comprise the mass of most organisms –Oxygen, carbon, hydrogen, and nitrogen • In addition, other elements, such as calcium , phosphorus , sulfur , and trace elements are present . . . • The periodic table is a chart of the elements arranged by atomic number C arbon H ydrogen O xygen N itrogen P hosphorus S ulfur http://gpc.edu/~pgore/PhysicalScience/periodic-table.gif The atomic mass of an atom Is a number that indicates how much matter it contains (Essentially, Protons + Neutrons ) Is expressed by the atomic mass unit (amu), also known as the Dalton Isotopes •Are two or more forms of atoms of the same element •Contain the same number of protons and electrons, but the number of neutrons varies • Radioisotopes break down and emit radiation Carbon Isotopes • Covalent bonds – Shared electrons between atoms – Bond can be single, double, or triple http://www.astro.lsa.umich.edu/~cowley/bonds.gif http://www.bluwavehybrid.com/files/WaterMolecule2.jpg 2 electrons = one covalent bond • Covalent bonds – Shared electrons between atoms – Bond can be single, double, or triple Partial charges Electronegativity Polarity • Ionic bonds – Electrostatic attraction between charged atoms – Example: Table salt (sodium chloride) • A chemical formula describes the...
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This note was uploaded on 02/24/2011 for the course BIO 110 taught by Professor Fairchild during the Fall '07 term at West Chester.

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LifeisChemistry - Life is chemistry Atoms and Molecules The...

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