Electron Sharing in Covalent Bonds

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Electron Sharing in Covalent Bonds
8.1 Formation of Covalent Bonds (SB p.203)
electrostatic
The shared electron pair spends most of the time
between the two nuclei.
Overlapping of atomic orbitals ? covalent bond
formation
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H 1s1 Overlapping between two 1-s orbitals H
1s e- from another H
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Electron density map of H2
Electron density map of NaCl
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Formation of Covalent bond by overlapping of
orbitals
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Octet Rule and its limitations
8.1 Formation of Covalent Bonds (SB p.206)
BF3
B small atomic size high I.E.s required to
become a cation.
Why doesnt B form ionic compounds with F?
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Octet Rule and its limitations
8.1 Formation of Covalent Bonds (SB p.207)
PCl5
There is low-lying vacant d-orbital in P.
Why Phosphorus can expand its octet to form PCl5?
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Dative Covalent Bonds
8.2 Dative Covalent Bonds (SB p.208)
The dative covalent bond (also known as the
coordinate bond) is a type of covalent bond in
which the shared pair of electrons is supplied by
only one of the bonded atoms.
Remarks(1) The atom that supplies the shared
pair of electrons is known as the donor
while the other atom involved in the dative
covalent bond is known as the acceptor. (2) Once
formed, a dative covalent bond cannot be
distinguished from a normal covalent bond.
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NH3BF3 Molecule
8.2 Dative Covalent Bonds (SB p.208)
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Ammonium Ion (NH4)
8.2 Dative Covalent Bonds (SB p.209)
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Aluminium Chloride Dimer (Al2Cl6)
8.2 Dative Covalent Bonds (SB p.209)
Al relative small atomic size high I.E.s
required to become a cation of 3 charge.
AlCl3
(a dimer of AlCl3)
Why doesnt Al form ionic compounds with Cl?
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8.4 Estimation of average covalent bond enthalpies
1.By average of ?Hatom Determine the ?Hatom
from successive bond dissociate enthalpy (p.210)
or from Hesss law (p.213)
p.210 from successive bond dissociate enthalpy
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8.4 Estimation of average covalent bond enthalpies
E(C-H) ?Hatom(CH4) / 4 1662/4 415.5 kJ
mol-1
1.By average of ?Hatom
2.By compare ?Hatom of two compounds
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2C(g) 6H(g)
?H 2696 (2820) -124 kJ mol-1