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Shapes of Molecules. Steric number of 5. Like PF 5 Phosphorus pentafluoride. F F F P F F . Would look like. This is called Trigonal Bipyramidal. Steric # 5 with unbonded pairs of electrons. With one pair of unbonded electrons it is a See-saw shape (SF 4 , IOF 4 )
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Steric number of 5 Like PF5 Phosphorus pentafluoride F F F P F F Would look like This is called Trigonal Bipyramidal
Steric # 5 with unbonded pairs of electrons • With one pair of unbonded electrons it is a See-saw shape (SF4, IOF4) • With two pairs of unbonded electrons it is T-Shaped (ClF3, BrF3) • With 3 unbonded pairs of electrons it is linear (XeF2)
Steric number of 6 Like SF6 sulfur hexafluoride Would look like F F F S F F F *remember really electronegative elements can break the octet rule This shape is Octahedral
Steric # of 6 with unbonded pairs of electrons • With one unbonded pair of electrons it is square pyramidal. (XeOF4) • With two unbonded pairs of electrons it is square planar. (XeF4)
Major difference • Covalent bonding is a sharing of electrons, Ionic bonding is a transfer of electrons. • Covalent bonds are stronger than ionic bonds because there is actually an electron going between them. • Therefore, it is harder to break a covalent bond than it is to break an ionic bond. • This is why we didn’t dissociate the polyatomic ions, they are held together with covalent bonds.
Shortcut to determining type of bond • When a metal and nonmetal bond you get an ionic bond • ~ something from the left excluding H bonds with something from the right = ionic bond. • When two nonmetals bond you get a covalent bond • ~things from the right bond with each other =covalent bond. • Metals don’t bond with each other.
Why this works • Electronegativity- ability of an atom to attract and hold bonding electrons. • Elements with a large difference in electronegativity will form an ionic bond, elements with a small difference will form covalent bonds.