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Chapter 8 Covalent Bonding. Molecular Compounds. Ionic Compounds- Review. atoms that lose or gain electrons become ions cations have + charge anions have – charge cations and anions are attracted to each other by elecrostatic force. bonds between ions form repeating patterns
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Chapter 8Covalent Bonding Molecular Compounds
Ionic Compounds-Review • atoms that lose or gain electrons become ions • cations have + charge • anions have – charge • cations and anions are attracted to each other by elecrostatic force.
bonds between ions form repeating patterns • can take the form of crystals when solid • usually a metal with a nonmetal • formula units, NOT molecules
Metallic Bonds Review • “sea of electrons” • sharing of electrons between atoms of the same metal (different metals would be alloys) • characteristics of metals are a result of this sharing of electrons • most common in the transition metals (d-block)
Reviewing the Octet Rule • outer electrons (the highest energy level electrons) are called valence electrons. • the most stable valence electron configuration is that of noble gases (8). • every atom will attempt to have its valence electrons conform to noble gas nearest it. • for most elements, this means the atom will have s2 and p6 filled when stable
formed by two or more nonmetals • molecules are a neutral group of atoms joined by covalent bonds in order to satisfy the octet rule (there are exceptions to this) • atoms are held together by sharing electrons • diatomic molecules are two of the same atoms covalently bonded
atoms of different elements can covalently bond to form molecular compounds • tend to have lower melting and boiling points than ionic compounds
often there is a pair of valence electrons that are not shared (unshared pair)
double or triple bonds share two or three pairs of electrons
Coordinate covalent bonds • instead of each atom contributing one electron to be shared, one atom contributes both bonding electrons
Molecular Formulas • shows how many atoms of each element • methane is one carbon and four hydrogen • CH4 • does not tell you about the molecule’s structure (structural formula)
Resonance • refers to the idea that there are two or more valid electron dot formulas for a molecule or ion