CHM136H1 Lecture Notes - Lecture 2: Molecular Orbital Theory, Ethane, Headon
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CHM136H1 Full Course Notes
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Indicating covalent bonds: lewis structures show valence electrons of an atom as dots. H has one dot, representing its 1s electron. Non-bonding electrons: valence electrons not used in bonding are called non-bonding electrons, or lone-pair electrons. Nitrogen atom in ammonia [nh(3)]: shares six valence electrons in three covalent bonds and remaining two valence electrons are nonbonding lone pair. Lone pairs are not always shown in diagrams. Electrons paired in overlapping orbitals and attracted to nuclei of both atoms. H-h bond results from overlap of two singly occupied 1s orbitals. H-h bond cylindrically symmetrical (cs); sigma bond (all sigma bonds are cs) Bond energy: reactions 2h- h(2) releases 436 kj/mol, product has 436 kj/mol less energy than two atoms: h-h has bond strength of 436 kj/mol (exothermic reaction) [spp=sp(2): sp(2) orbitals are in a plane with 120 degree angels, remaining p orbital is perpendicular to the plane.
