VSEPR and Geometry
Define electron domains and predict the shape for SF6.
SF6 has 6 bonding electron domains, no lone pairs → Octahedral shape, bond angle 90°
What is a sigma bond?
A single covalent bond formed by head-on overlap of atomic orbitals.
What is resonance? Give an example.
Resonance is the delocalization of electrons via multiple contributing structures; example: ozone (O3).
State the hybridisation of carbon in methane.
Carbon in methane is sp3 hybridized.
Define electronegativity. Give an example.
Electronegativity is the ability of an atom to attract electrons; fluorine is highly electronegative.
Give the bond angle in PCl5 and its geometry.
PCl5 has trigonal bipyramidal shape with bond angles 90° (axial-equatorial) and 120° (equatorial-equatorial).
Which molecules have only sigma bonds?
Molecules like methane (CH4) have only sigma bonds.
Draw resonance structures for O3.
O3 has two resonance structures with one double and one single bond alternating.
Describe the hybridisation in ethene (C2H4).
Carbons in ethene are sp2 hybridized.
Explain how polar covalent bonds differ from ionic bonds.
Polar covalent bonds involve unequal sharing of electrons; ionic bonds involve electron transfer.
Name one molecule with an expanded octet and its geometry.
SF4, seesaw shape; XeF4, square planar shape.
How many pi bonds are in benzene?
Benzene has 6 pi bonds due to delocalized electrons over 6 carbon atoms.
How does delocalization affect bond length in benzene?
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Delocalization equalizes bond lengths, making all C-C bonds intermediate between single and double
Draw sp hybridisation using an example.
In ethyne (C2H2), carbons are sp hybridized with linear geometry.
Which factors affect metallic bond strength
Charge density of metal ions and number of delocalized electrons.
Draw and predict bond angles for XeF4.
XeF4 has 4 bonded atoms and 2 lone pairs → square planar shape, bond angles 90°.
Distinguish between sigma and pi bonds with diagrams.
Sigma bonds result from axial overlap; pi bonds result from sideways overlap of p orbitals.
Why does CO3^2- have equivalent C-O bonds?
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Resonance delocalizes electrons over all C-O bonds, making them equivalent in length and strength
Relate hybridisation to geometry in ethyne (C2H2).
sp hybridization causes linear molecule with 180° bond angle.
Use the bonding triangle to position AlCl3.
AlCl3 is polar covalent, lying between covalent and ionic bonding on the triangle.
500: Explain formal charge and select the preferred Lewis structure for SO2.
Preferred structure minimizes formal charges with one double and one single bond, and a lone pair on S.
How do sigma and pi bonds impact the strength of double bonds?
Double bonds consist of one sigma and one pi bond; pi bonds add strength but are weaker than sigma bonds.
Describe delocalization in graphite and its impact on conductivity.
Delocalized electrons between layers enable free electron movement, giving graphite electrical conductivity.
Explain how hybridisation changes for N in NH3 vs N2.
N in NH3 is sp3 hybridized (pyramidal shape, lone pair); N in N2 is sp hybridized with triple bond.
Compare properties of allotropes of carbon: diamond, graphite, graphene.
Diamond is sp3 tetrahedral and hard; graphite is sp2 planar and conductive; graphene is single-layer conductive.