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Objectives. Define chemical bond.Explain why most atoms form chemical bonds.Describe ionic and covalent bonding.Explain why most chemical bonding is neither purely ionic nor purely covalent.Classify bonding type according to electronegativity differences.. Section 1 Introduction to Chemical Bonding.
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1. Chapter 6 Chemical Bonding
3. Chemical Bond – atoms bound together by a mutual electrical attraction between nuclei and valence electrons Ionic Bond – bond between anions (-) and cations (+) caused by the transfer of electrons between atoms – usually a metal and a nonmetal
Covalent Bond – bond between atoms that share valence electrons – usually 2 nonmetals
Metallic Bonding – attraction between metals with delocalized electrons – (not a real bond)
Hydrogen Bond – attraction that occurs between hydrogen atoms in a compound and strongly electronegative atoms with lone pairs of electrons (oxygen, nitrogen, etc.) (not a real bond)
5. Predicting Bond Type by Electronegativity Difference
9. Molecule –
Compound –
Chemical Formula –
Molecular Formula –
.
10. Covalent Bond Characteristics Bond Length – average distance between two bonded atoms at their minimum potential energy
Bond Angle – angle between three bonded atoms
Bond Energy – energy required to break a chemical bond and form neutral isolated atoms
12. Lewis Structures Structural Formula – shows the kind, number and arrangement of atoms in a molecule (may or may not show lone pairs)
Octet Rule – compounds tend to form so that both atoms have eight electrons in their outer energy level
Exceptions – hydrogen & expanded octets
Electron Dot Notation – Lewis Dots – shows valence electrons
13. Rules for Drawing Lewis Structures Determine the type and number of atoms
Determine the total number of valence electrons available to bond
Draw skeletal structure (least electronegative atom is usually central)
Draw bonds
Place extra electrons to fill octet
Check or recount electrons to make sure everything is “HAPPY”
14. Simple Structures
15. More Single Bonds
16. Multiple Covalent Bonds
17. Resonant Structures – two or more possible structures for the same molecule
19. Ionic Compounds – positive and negative ions combined in such a way that the net charge is 0
Formula Unit – simplest collection (ratio) of atoms in an ionic compound
20. I o n i c B o n d s
21. Crystal Lattice – orderly arrangement of an ionic crystal
22. Basic Lattice Systems
23. Properties of Bond Types Covalent Molecules
Low melting points
Low boiling points
insulators Ionic Compounds
High melting points
High boiling points
Conductors when molten
24. Polyatomic Ions – a group of covalently bonded atoms that has a charge
26. Metallic Bonding – attraction between metals with delocalized electrons – (not a real bond) Properties
Good conductors of heat and electricity
Good reflectors (shiny)
Malleable
Ductile
High tensile strength
29. Molecular Geometry – Valence Shell Electron Pair Repulsion Theory – Predicts shapes of molecules based on the repulsion of unshared pairs of electrons (lone pairs)
33. Examples
35. – mixing of two or more orbitals of similar energies to make orbitals with the same energy
36. – molecules that have a positive and negative ends due to the arrangement of bonds and lone pairs
37. forces of attraction between molecules that are weaker than bonds
39. Homework Page 209-211
Numbers 3,5,6,15,16,20,21,23,24,25,28,29,31,38,46 48,49