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Unformatted text preview: ond order is calculated from the
molecular orbital energy diagram (bond order is the difference between the number of
bonding electrons and the number of antibonding electrons divided by two).
Paramagnetic: a kind of induced magnetism, associated with unpaired electrons, that causes a
substance to be attracted into an inducing magnetic field. Diamagnetic: a type of induced
magnetism, associated with paired electrons, that causes a substance to be repelled from the
inducing magnetic field. The key is that paramagnetic substances have unpaired electrons in
the molecular orbital diagram, whereas diamagnetic substances have only paired electrons in
the MO diagram.
To determine the type of magnetism, measure the mass of a substance in the presence and
absence of a magnetic field. A substance with unpaired electrons will be attracted by the
magnetic field, giving an apparent increase in mass in the presence of the field. A greater
number of unpaired electrons will give a greater attraction and a greater observed mass
increase. A diamagnetic species will not be attracted by a magnetic field and will not show a
mass increase (a slight mass decrease is observed for diamagnetic species). 36. Considering only the 12 valence electrons in O2, the MO models would be: $2p*
! ! !" !" # 2p* !" # 2p !" !" !" $2p !" !" *
$2s !" !" $2s !" O2 ground state Arrangement of electrons consistent
with the Lewis structure (double bond
and no unpaired electrons). It takes energy to pair electrons in the same orbital. Thus the structure with no unpaired
electrons is at a higher energy; it is an excited state. CHAPTER 14 COVALENT BONDING: ORBITALS 583 38.
The localized electron model does not deal effectively with molecules containing unpaired
electrons. We can draw all of the possible structures for NO with its odd number of valence
electrons but still not have a good feel for whether the bond in NO is weaker or stronger than
the bond in NO−. MO theory can h...
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