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Covalent Bonding http://charlescurtis.ca Ratio of Atoms in Covalently Bonded Molecules In Ionic compounds the molecular formula represents the repeating pattern (ratio of atoms). In Covalent Compounds the molecular formula give information regarding one full unit. Ionic Example: NaCl We do not have one molecule containing one sodium atom and one chlorine atom. NaCl represents ratio of Na to Cl. NaCl will always give the same structure Covalent Bonding Example Acetone – C3H6O Allyl Alcohol - C3H6O Demo The power of acetone D-Glucose Drawing Lewis Structures for Covalently Bonded Compounds Draw Lewis Symbols as in Ionic Compounds Instead of stealing elections the atoms share Shared electrons are represented by a dash HF The stable octet is achieved by sharing electrons. Octet Rule In Ionic bonding electrons are gained or lost. In Covalent bonding electrons are shared. Fluorine Gas Why am I not drawing any symbols with square brackets as I did on Monday? Example with more than one bond Predicting # of Bonds The number of bonds can be predicted by counting the number of single valence electrons. Atom Valence e- Single e- Carbon 4 4 Nitrogen 5 3 Oxygen 6 2 Chlorine 7 1 Single, Double or Triple Covalent bonds and contain one pair, two pairs or three pairs of bonding electrons. One pair = single bond (Sigma bond) σ Two pairs = double bond (second Pi bond) π Three pairs = triple bond (third Pi bond) π Structural Formula Similar to the Lewis Structure but without the electrons. Just show atomic symbols and the covalent bonds. Work on Question #1 page 77. We will go over together in 10 min. Correction (error in book) Draw a Lewis structure and write the structural formula for each of the following: Coordinate Covalent Bonding Is a covalent bond, where both the shared electrons come from one atom. Covalent vs Ionic Covalent Bonds are stronger Covalent Molecules weakly interact with other covalent molecules so the melt/boil at lower temperatures. Ionic Compounds form conductive solutions whereas molecular one tend to not form conductive solutions. Intermolecular vs Intramolecular What does Intermolecular forces mean? – Attractive forces between different molecules or ions. What are Intramolecular forces? – Attractive forces between atoms within the same compounds. Please pages 79 and 80 in aid in completing your homework. Homework p79 #2 p80 #3,4 p81 #6,10,11,13,14 Hints: Question #10 read p 79 Please read over all questions before you leave so you can get help on difficult questions.
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