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Covalent Bonding

Covalent Bonding. Objectives: 1. Describe the characteristics of a covalent bond. 2. Describe the difference between polar and nonpolar covalent bonds. Key Terms:

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Covalent Bonding

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  1. Covalent Bonding Objectives: • 1. Describe the characteristics of a covalent bond. • 2. Describe the difference between polar and nonpolar covalent bonds. Key Terms: • Molecule, molecular substance, molecular formula, structural formula, Lewis structure, unshared pair, single covalent bond, double covalent bond, triple covalent bond, polar, nonpolar

  2. Covalent Bonds • A covalent bond is one where the electrons are shared. • A group of covalently bonded atoms is called a molecule. • These molecular substances include DNA, sugar and carbon dioxide. The molecules can contain as few as 2 atoms and as many as a million. • Rules for covalent bonds: • electrons are shared in covalent molecules • covalently bonded molecules follow the octet rule (some exceptions - BF3) • atoms will share electrons in order to fill their valence orbitals • covalent molecules can form single, double, or triple bonds • covalent bonds can be rearranged to form different molecules (glucose, fructose, & maltose)

  3. Properties of Molecules • relatively low boiling points • present in all phases • poor conductors of heat and charge • usually dull in appearance • not malleable or ductile

  4. Types of Covalent Bonds • Most covalent bonds are slightly polar in nature • Electrons are unequally shared between atoms due to electronegativity differences between the atoms • < 0.4 non-polar covalent • 0.4 – 1.9 polar covalent • > 1.9 ionic Example: Water (H2O) • electronegativity of H = 2.1 • electronegativity of O = 3.5 • Difference 3.5 – 2.1 = 1.4 polar covalent

  5. Formulas - Empirical • lists atom ratios in the ratios that are present in the molecules • not good for describing covalently bonded molecules • (CH2O)n is wood, sugar, lactic acid, etc ...

  6. Formulas - Molecular • lists the atoms in the found in the molecule without reducing • better that the empirical formula but not the best for describing molecules • C6H12O6 - fructose, C6H12O6 - glucose, C6H12O6 - galactose

  7. Formulas - Structural • shows where the individual atoms are bonded • Lewis structures are an example of this type of formula • Dashes are a shorthand way of showing bonds • Each represents 2 electrons

  8. Formulas – Ball-n-Stick • shows the 3 dimensional structure of the molecule

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