Shapes Of Molecules. Flashcards

0
Q

What a lone pairs?

A

These are pairs of valent electrons that are not being used in bonding.

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1
Q

What are bonding pairs?

A

These are the pair of electrons shared by two atoms joined in a covalent bond.

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2
Q

What is the V.S.E.P.R principle?

A

This sums up the reasons for molecular shapes.

Pairs of electrons take up positions around the central atom so that there is minimum repulsion between them.

Lone pair-lone pair repulsion > lone pair-bond pair repulsion > bond pair-bond pair repulsion.

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3
Q

Why do lone pairs exert a stronger repulsive force than bond pairs?

A

Because they are only attracted by one nucleus so the electron clous shape is shorter and fatter than a bonding pair of electrons which is held by two nuclei.

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4
Q

How can we predict the shape of any simple molecule?

A

By applying three rules:

All pairs of electrons contribute to the overall shape of the molecule by taking up positions as far apart as possible around the central atom

Lone pairs of electrons exert a bigger repulsive force than bonding pairs of electrons

Multiple bonds are regarded as consisting of one electron pair only.

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5
Q

What is the shape and angle present for a molecule with a V.S.E.P.R value of 2?

A

Shape - linear

Bond angle 180°

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6
Q

What is the shape and angle present for a molecule with a V.S.E.P.R value of 3?

A

Shape - Triganol planar.

Bond angle - 120°

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7
Q

What is the shape and angle present for a molecule with a V.S.E.P.R value of 4?

A

Shape - tetrahedral

Bond angle - 109.5°

Exceptions. (Due to presence of lone pairs)

NH₃
Shape - pyramidal
Bond angle - 107°

H₂O
Shape - Bent
Bond angle - 104°

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8
Q

What is the shape and angle present for a molecule with a V.S.E.P.R value of 5?

A

Shape - trigonal bi-pyramidal

Bond angles - 90° and 120°

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9
Q

What is the shape and angle present for a molecule with a V.S.E.P.R value of 6?

A

Shape - octahedral

Bond angle - 90°

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