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Chapter 6 Covalent Compounds

Chapter 6 Covalent Compounds. What are covalent compounds? compound in which atoms are bonded together by the sharing of electrons Also known as molecular compounds What is the Bond called? Covalent Bond- bond formed from the sharing of electrons -occurs between 2 nonmetals.

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Chapter 6 Covalent Compounds

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  1. Chapter 6Covalent Compounds • What are covalent compounds? • compound in which atoms are bonded together by the sharing of electrons • Also known as molecular compounds What is the Bond called? Covalent Bond- bond formed from the sharing of electrons -occurs between 2 nonmetals

  2. Electronegativity • Measure of how much an element pulls electrons away from other elements • metals have low electronegativities • Nonmetals have high electronegativities

  3. Properties of Covalent Compounds • Lower melting and boiling points than ionic compounds • Soft and squishy(usually) • More flammable • Do not conduct electricity in water • Usually not soluble in water

  4. Using Electronegativity to predict the type of bond If the difference •  0.3  Nonpolar covalent bond - the bonding electrons are shared equally between 2 bonding atoms • 0.3 – 1.7 Polar covalent bond - the bonding electrons are more strongly attracted by one of the bonding atoms 3.  1.7 Ionic bond

  5. How can you show the sharing of electrons? • By using Lewis Structures • diagram showing the arrangement of valence electrons among the atoms in a molecule • It represents a chemical formula

  6. Steps for drawing Lewis Structures for no charged atoms • Count the total valence electrons for the molecule  “has” column • Determine octet electrons  “want” column • Subtract the valence electrons from octet electrons # bonding electrons • Divide by 2(each bond has 2 e-) # bonds • Draw the structure with the # of bonds

  7. con. • Find unshared pairs by subtracting bonding electrons from valence electrons and arrange around the atoms to satisfy the octet rule • Central atom usually a small electronegativity value

  8. Handy Rules • Hydrogen and halogens bond once • Oxygen bonds twice • Nitrogen and Boron bond 3 times • Carbon bonds 4 times Let’s determine the Lewis structure for the following compound: CH3I

  9. Double and Triple Bonds • Double Bond- sharing 2 pairs of electrons • Triple Bond- sharing 3 pairs of electrons

  10. Resonance • Having more than one possible Lewis structure • Let’s look at ozone, O3 and silicon dioxide, SiO2.

  11. Lewis Structures for Polyatomic Ions Let’s look at ammonium, NH4+. Try these in your notes, ClO3- and SO42-.

  12. Naming Covalent(molecular) compounds • First element name first, full name./ • Second elementroot + “ide” • Use prefix to denote the # of atoms • Mono is not used in the first element Prefixes Mono 1 hexa 6 Di 2 hepta 7 Tri 3 octa 8 Tetra 4 nona 9 Penta 5 deca 10

  13. Oxidation Numbers • Apparent or imaginary charge given to an atom General Rules Oxidation # • Any free element 0 ex: Na, O2, H • Monoatomic ion same as charge • Fluorine -1 • Oxygen -2 • Hydrogen +1 • Group 1,2 and Al +1,+2, +3

  14. Molecular Formula • Gives the type and actual # of atoms • multiple of the empirical formula Determining the Molecular Formula • Determine the empirical formula • Determine the empirical formula mass • Divide the molecular formula mass by the empirical formula mass • Multiply the empirical formula by this factor

  15. Molecular formula example • Determine the molecular formula of a compound that has the following composition: 76.54% C, 12.13% H, 11.33% O Its molar mass is 282.45 g/mol.

  16. Polymers • Large chainlike molecules composed of smaller molecules called monomers • What are structural Formulas? • Shows the spatial arrangement of atoms and bonds within a molecule

  17. Predicting the Shape of a Molecule • VSEPR Theory(valence shell electron pair repulsion) • Based on the idea that pairs of valence electrons surrounding an atom repel each other

  18. VSEPR rules • Draw the Lewis structure • Count the # of electron clouds around the central atom a. Single, double , triple bonds= 1 electron cloud b. Unshared pairs = 1 electron cloud Bonded atoms determines the shapegeometry Unshared pairs  bond angle 3. Determine the shape

  19. VSEPR Shapes Bonding Unshared PairsPairsGeometry 2 0 Linear 3 0 Trigonal Planar 2 1 Bent 4 0 Tetrahedral 3 1 Trigonal pyramidal 2 2 Bent

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