bonding - quia · metallic hydrogen/dipole van der waals. classification of bonds ... in an ionic...
TRANSCRIPT
Date
Bonding
Overview
✤ What are bonds?
✤ Types of Bonds
✤ Ionic or Covalent?
✤ Drawing Bonds
✤ Naming Compounds
Bonds
✤ An attachment between atoms.
✤ Bonds have to do with the electrons (particularly the outside ones) in atoms.
✤ The amount of attraction between the atoms is related to the strength of the bond.
✤ Generally, bonds form so that atoms can achieve eight valence electrons (octet rule).
Classification of Bonds
Chemical Bonds
Secondary (weak)
Primary (strong)
ionic
covalent
metallic hydrogen/dipole
Van der Waals
Classification of Bonds
✤ Bonds
✤ ionic
✤ covalent
✤ metallic
Ionic Bonds✤ When atoms combine, they do so by trying to achieve an inert (noble)
gas configuration. In an ionic bond, one gives up electron(s).
✤ In an ionic bond, a cation is attracted to an anion.
✤ Sodium Chloride is a classic example (NaCl). Notice the Lewis Diagram
Covalent Bonds
✤ Covalent bonding involves the sharing of one or more pairs of electrons so that each molecule achieves an inert gas configuration.
✤ Hydrogen is a classic example is H2
Metallic Bonds
✤ The valence electrons become detached from the nucleus of individual atoms and are shared (like covalent). The positive ions are closely packed within a sea of delocalized electrons.
✤ They form between metals.
✤ Metals are malleable because they can slide over each other without breaking more bonds than are made.
✤ Ionic compounds are formed between metals on the left of the periodic table and non-metals on the right side. Generally groups 1-3 and 5-7. What is the difference in their electronegativity? Examples:
✤ Al and F in AlF3
✤ Al and Cl in Al2Cl6
✤ Al and O in Al2O3
✤ Al and Br in Al2Br6
Ionic or Covalent?
✤ If the electronegativity difference is greater than 1.7 to 1.9, the bond will be more ionic than covalent.
✤ Al and F (2.6) --> ionic
✤ Al and Cl (1.4) --> covalent
✤ Al and O (2.0) --> ionic
✤ Al and Br (1.3) --> covalent
Ionic or Covalent?
Drawing Lewis Diagrams for the Formation of Compounds
✤ It’s different for ionic and covalent compounds.
✤ Shows the charges and orientation of atoms... very useful
✤ How do we do it?
Homework
✤ Read about ionic and covalent bonds and their relation to electronegativity (227-241).
✤ Do “Lewis Diagrams of Ionic and Covalent Compounds”