mcneil assignment 5

7/24/2019 Mcneil Assignment 5

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1a)

HF is a heteronuclear atom which exhibits a polar covalent bond. The orbitals no

longer have equal density on each atom.

i) either bonding, non-bonding, or antibondingii) either Hlocalied, primarily H-character, primarily F-character, or F-

localied.To arrive at your answers, consider the nature and relative energies o! the

atomic orbitals that overlap to !orm each molecular orbital.

a)

1" # i) non $onding. ii) %rimarily F&s in character. HF is a heteronuclear atom which

exhibits a polar covalent bond. The orbitals no longer have equal density on each

atom. The high 'uorine localiation o! this orbital is a consequence o! the high

electronegativity o! 'uorine.

&" # i) $onding ii) F-localied. Has both H1s and F&p character. HF is a

heteronuclear atom which exhibits a polar covalent bond. The orbitals no longerhave equal density on each atom. The high 'uorine localiation o! this orbital is a

consequence o! the high electronegativity o! 'uorine. There is (s * # p *+ overlap

in this molecular orbital.

1 # i) nonbonding ii) %rimarily F-character - Fluorine &p in character. These orbitals

exist in the 'uorine atom. They analogous to &p 'uorine *+s. They are not involved

in bonding. They aren+t involved in anti-bonding either. They are non-bonding.


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Fluorine &p &p/ . 0un perpendicular to H-F axis (+. 2o not overlap 3-orbital. 2o

not participate in anti-bonding with it either. There!ore nonbonding.

4" # i) anti-bonding ii) H-localied. The H13 * has relatively high energy when

compared to the 'uorine orbitals. There!ore, the hydrogen+s 13 orbital contributes

predominantly to the high-energy antibonding 5*.

b)

1" and &" 5*+s are F-localied due to the electronegativity o! F in the 5*

orbital

1 - is non-bonding but is !luorine &p in character. There!ore, e-

occupying this 5* will inhabit the & p-orbitals o! 'uorine.

4" # ntibonding, unoccupied, 675*. %rimarily H 1s * orbital

characteristic. 3ince unoccupied no e8ect on molecular polarity. nti-bonding 5* - would destable molecule i! occupied.

494 occupied 5*+s have the ma:ority o! charge based on the 'uorine. ny

given molecule has characteristics o! an average o! the sum o! it+s 5*+s.

There!ore, the entire H-F molecule is polar because 494 occupied 5*+s

exhibit electron density on the 'uorine.

c) Fluorine &p &p/ . 0un perpendicular to H-F axis (+. 2o not overlap

3-orbital. 2o not anti-overlap it either. There!ore nonbonding.

d) 5* description completely agrees. Has 1 bonding pair localied to the

electronegative 'uorine and 4 electron pairs based on the 'uorine which

do not participate in bonding.& e- enter the & " orbital, !orming a bond between H F atoms. %olar

bond is localied on F atom.& e- enter into the 1 " orbital which is largely non-bonding and con!ined to

F atom.; e- enter the 1-pi orbital which are non-bonding and con%0 do however agree in that the number o! bonding and F-localied

nonbonding pairs are numerically equivalent.

&)


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a) ?arbon has ; valence e-. The photoelectron spectrum o! methane

shows a pea@ at 14e= and a pea@ approximately A194) o! the sie at &4 e=.

=3>%0 assumes all valenec bonds are equal in energy. This is not the case

in this photoelectron spectrum. 4 valence bonds o! carbon lie in one

energy level and one lies in an energy level in which more energy is

needed to brea@ the bond. This is to say that, in methane, 4 pairs o!

bonding e- occupy 4 degenerate orbitals and one pair o! bonding electrons

occupies a bonding s-orbital which is harder to extract

?arbon has !our valence electrons. *ne in a &s orbital and 4 in &p orbitals.

mcneil assignment 5

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