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Chemistry 8.2. 8.1. Molecules and Molecular Compounds. Bell Work How would you combine the following: Ca 2+ PO 4 3-. 8.1. Molecules and Molecular Compounds. A molecule: atoms joined together by covalent bonds (shared). Neutral.
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8.1 Molecules and Molecular Compounds Bell Work How would you combine the following: Ca2+ PO43-
8.1 Molecules and Molecular Compounds • A molecule: atoms joined together by covalent bonds (shared). Neutral. • A diatomic molecule: a molecule consisting of two atoms. Rule of 7’s.
8.1 Molecules and Molecular Changes • Molecular compounds tend to have relatively lower melting and boiling points than ionic compounds.
8.2 The Octet Rule in Covalent Bonding • Molecules are made up of non-metals held together by covalent bonds.
Which of the following has the highest melting point? a) NO2 b) CaBr2 c) CH4
8.2 The Octet Rule in Covalent Bonding • In covalent bonds, atoms SHARE electrons to obtain noble gas electron configurations.
8.2 Single Covalent Bonds • Single Covalent Bonds • How can we show covalent bonds with electron dot structures?
8.2 Single Covalent Bonds • Two atoms held together by sharing a pair of electrons are joined by a single covalent bond.
8.2 Single Covalent Bonds • An electron dot structure such as H:H represents the shared pair of electrons of the covalent bond by two dots. • A structural formula represents the covalent bonds by dashes (H-H) and shows the arrangement of covalently bonded atoms.
8.2 Single Covalent Bonds • The halogens form single covalent bonds in their diatomic molecules. Fluorine is one example.
8.2 Single Covalent Bonds • A pair of valence electrons that is not shared between atoms is called an unshared pair or Lone Pair.
8.1 Section Assessment
8.1 Section Assessment
8.2 Double and Triple Covalent Bonds • A bond that involves two shared pairs of electrons is a double covalent bond. • A bond formed by sharing three pairs of electrons is a triple covalent bond.
8.2 Double and Triple Covalent Bonds
8.2 Coordinate Covalent Bonds • Coordinate Covalent Bonds • How are coordinate covalent bonds different from other covalent bonds?
8.2 Coordinate Covalent Bonds • In carbon monoxide, oxygen has a stable configuration but the carbon does not.
8.2 Coordinate Covalent Bonds • As shown below, the dilemma is solved if the oxygen donates one of its unshared pairs of electrons for bonding.
8.2 Coordinate Covalent Bonds • A coordinate covalent bond is a covalent bond in which one atom contributes both bonding electrons. • Shown by arrows
8.2 Coordinate Covalent Bonds • A polyatomic ion, such as NH4+, is a tightly bound group of atoms that has a positive or negative charge and behaves as a unit. • Most plants need nitrogen that is already combined in a compound to grow.
8.2 Coordinate Covalent Bonds
8.2 Section Assessment
8.2 Section Assessment
8.2 Bond Dissociation Energies • Bond Dissociation Energies • How is the strength of a covalent bond related to its bond dissociation energy?
8.2 Bond Dissociation Energies • The energy required to break the bond between two covalently bonded atoms is known as the bond dissociation energy. • A large bond dissociation energy corresponds to a strong covalent bond.
8.2 Section Quiz. • 8.2.
8.2 Section Quiz. • 1. In covalent bonding, atoms attain the configuration of noble gases by • losing electrons. • gaining electrons. • transferring electrons. • sharing electrons.
8.2 Section Quiz • 2. Electron dot diagrams are superior to molecular formulas in that they • show which electrons are shared. • indicate the number of each kind of atom in the molecule. • show the arrangement of atoms in the molecule. • are easier to write or draw.
8.2 Section Quiz • 3. Which of the following molecules would contain a bond formed when atoms share three pairs of electrons? • Se2 • As2 • Br2 • Te2
