Define VSEPR theory .

VSEPR theory (Valence Shell Electron Pair Repulsion theory) states that electron pairs around a central atom repel each other and arrange themselves as far apart as possible to minimise repulsion, determining the shape of the molecule.

State the three key rules of VSEPR theory.

All electron pairs (bonding and lone pairs) spread out as far apart as possible. Lone pairs repel more strongly than bonding pairs . Multiple bonds behave like a single electron domain when determining shape.

True or False? Lone pairs repel neighbouring electron pairs more strongly than bonding pairs do.

True. Lone pairs are held closer to the nucleus and spread over a larger region of space, causing greater repulsion. This reduces bond angles compared to the regular geometry.

NH 3 has a .......... shape with a bond angle of .......... because one lone pair repels the bonding pairs, reducing the angle from 109.5°.

NH 3 has a trigonal pyramidal shape with a bond angle of 107° because one lone pair repels the bonding pairs, reducing the angle from 109.5°.

What shape and bond angle does SF 6 adopt, and why?

SF 6 adopts an octahedral shape with bond angles of 90° . Sulfur forms 6 single bonds with no lone pairs, so all six bonding pairs repel each other equally.

True or False? CO 2 has a bent shape because of lone pairs on the carbon atom.

False. CO 2 is linear (180°). Carbon has no lone pairs and forms two double bonds, each counted as one electron domain. The two domains arrange linearly.

PCl 5 has a .......... shape with bond angles of .......... (equatorial) and .......... (axial).

PCl 5 has a trigonal bipyramidal shape with bond angles of 120° (equatorial) and 90° (axial).

Why does H 2 O have a bond angle of 104.5° rather than the tetrahedral angle of 109.5°?

Oxygen in H 2 O has two lone pairs in addition to two bonding pairs. The lone pairs repel more strongly than bonding pairs, compressing the H-O-H bond angle from 109.5° to 104.5° .

True or False? BF 3 has a trigonal planar shape with bond angles of 120°.

True. Boron forms 3 bonding pairs and has no lone pairs. The three electron domains arrange with trigonal planar geometry , giving bond angles of 120° .

A LevelChemistryCambridge (CIE)Flashcards3. Chemical BondingShapes of Molecules

Shapes of Molecules (Cambridge (CIE) A Level Chemistry): Flashcards

Exam code: 9701

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FrontShapes of Molecules
Define VSEPR theory.
FrontShapes of Molecules
State the three key rules of VSEPR theory.
BackShapes of Molecules
All electron pairs (bonding and lone pairs) spread out as far apart as possible.
Lone pairs repel more strongly than bonding pairs.
Multiple bonds behave like a single electron domain when determining shape.

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Cards in this collection (9)

Define VSEPR theory.
VSEPR theory (Valence Shell Electron Pair Repulsion theory) states that electron pairs around a central atom repel each other and arrange themselves as far apart as possible to minimise repulsion, determining the shape of the molecule.
State the three key rules of VSEPR theory.
1. All electron pairs (bonding and lone pairs) spread out as far apart as possible.
2. Lone pairs repel more strongly than bonding pairs.
3. Multiple bonds behave like a single electron domain when determining shape.
True or False?
Lone pairs repel neighbouring electron pairs more strongly than bonding pairs do.
True.
Lone pairs are held closer to the nucleus and spread over a larger region of space, causing greater repulsion. This reduces bond angles compared to the regular geometry.
NH₃ has a .......... shape with a bond angle of .......... because one lone pair repels the bonding pairs, reducing the angle from 109.5°.
NH₃ has a trigonal pyramidal shape with a bond angle of 107° because one lone pair repels the bonding pairs, reducing the angle from 109.5°.
What shape and bond angle does SF₆ adopt, and why?
SF₆ adopts an octahedral shape with bond angles of 90°. Sulfur forms 6 single bonds with no lone pairs, so all six bonding pairs repel each other equally.
True or False?
CO₂ has a bent shape because of lone pairs on the carbon atom.
False.
CO₂ is linear (180°). Carbon has no lone pairs and forms two double bonds, each counted as one electron domain. The two domains arrange linearly.
PCl₅ has a .......... shape with bond angles of .......... (equatorial) and .......... (axial).
PCl₅ has a trigonal bipyramidal shape with bond angles of 120° (equatorial) and 90° (axial).
Why does H₂O have a bond angle of 104.5° rather than the tetrahedral angle of 109.5°?
Oxygen in H₂O has two lone pairs in addition to two bonding pairs. The lone pairs repel more strongly than bonding pairs, compressing the H-O-H bond angle from 109.5° to 104.5°.
True or False?
BF₃ has a trigonal planar shape with bond angles of 120°.
True.
Boron forms 3 bonding pairs and has no lone pairs. The three electron domains arrange with trigonal planar geometry, giving bond angles of 120°.

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