Chapter 6 - Shapes of Molecules and Intermolecular Forces

Question 1

What does molecular shape depend on?

Answer 1

Electron pairs around the central atom.

Question 2

In what way do electron pairs interact?

Answer 2

They repel each other.

Question 3

Which type of pair repels the most?

Answer 3

Lone pairs

Question 4

What is the order of pair repulsion, from strongest to weakest?

Answer 4

Lone pair/lone pair
Lone pair/bonding pair
Bonding pair/bonding pair

Question 5

What is the name of the way to predict a molecule’s shape?

Answer 5

Electron pair repulsion theory

Question 6

What shape name is given to a molecule with no lone pairs but four bonded pais?

Answer 6

Tetrahedral

Question 7

What is the bond angle in a tetrahedral molecule?

Answer 7

109.5

Question 8

whats the shapes table?

Answer 8

Question 9

what do dotted wedge, solid wedges and filled wedges stand for?

Answer 9

Question 10

What shape name is given to a molecule with one lone pair?

Answer 10

pyramidal

Question 11

What is the bond angle in a pyramidal molecule?

Answer 11

107

Question 12

What shape name is given to a molecule with two lone pairs?

Answer 12

Non-linear

Question 13

What is the bond angle in a non-linear molecule?

Answer 13

104.5

Question 14

What shape name is given to a molecule with 2 electron/bonded pairs around the central atom?

Answer 14

Linear

Question 15

What is the bond angle in a linear molecule?

Answer 15

180

Question 16

What shape name is given to a molecule with 3 electron pairs and no lone pairs around the central atom?

Answer 16

Trigonal planar

Question 17

What is the bond angle in a trigonal planar molecule?

Answer 17

120

Question 18

What shape name is given to a molecule with 5 electron pairs around the central atom?

Answer 18

Trigonal bipyramidal

Question 19

What is the bond angle in a trigonal bipyramidal molecule?

Answer 19

There are actually two, 120 in one plane and 90 in the other plane.

Question 20

What shape name is given to a molecule with 6 electron pairs around the central atom?

Answer 20

Octahedral

Question 21

What is the bond angle in an octahedral molecule?

Answer 21

90

Question 22

What is electronegativity?

Answer 22

An atom’s ability to attract the electron pair in a covalent bond.

Question 23

How is electronegativity measured?

Answer 23

On the Pauling scale.

Question 24

What does a higher Pauling value mean?

Answer 24

A higher electronegativity and thus a greater attraction for an electron pair in a covalent bond.

Question 25

What makes a bond polar?

Answer 25

Two atoms with electronegativities differing by at least 0.5, the bonding electrons are pulled towards the more electronegative atom, making it polar.

Question 26

What does a polar bond form?

Answer 26

A permanent dipole

Question 27

how are the more and less electronegative elements shown?

Answer 27

𝛿− is more electronegative 𝛿+ is less electronegative

Question 28

How is a dipole formed?

Answer 28

A difference in charge between the two atoms, caused by a shift in electron density in the bond.

Question 29

Are diatomic gases polar or non-polar, why?

Answer 29

Non-polar Because the atoms have equal electronegativities and so the electrons are equally attracted to both nuclei.

Question 30

What happens if the polar bonds are arranged symmetrically in a molecule?

Answer 30

The dipoles cancel each other out, so the molecule has no overall dipole and is non-polar.

Question 31

What happens if the polar bonds are arranged unsymmetrically in a molecule?

Answer 31

Uneven distribution of charge and the molecule will have an overall dipole.

Question 32

What can electronegativity be used to predict about bonding?

Answer 32

Whether it will be covalent or ionic bonding.

Question 33

What is the general strength of intermolecular forces?

Answer 33

Very weak

Question 34

What is the order of the intermolecular forces from strongest to weakest?

Answer 34

Hydrogen bonding Permanent dipole-dipole interactions Induced dipole-dipole

Question 35

What are induced dipole-dipole forces?

Answer 35

Electrons in clouds can at one moment be unevenly distributed, creating a temporary dipole. This dipole induces another dipole on a neighbouring atom and the two are attracted to each other. The dipoles can then be brought about in a domino effect. Overall the atoms are attracted to one another.

Question 36

What is the effect of stronger induced dipole-dipole forces?

Answer 36

Higher boiling points

Question 37

Why are higher boiling points brought about?

Answer 37

Larger molecules have larger electron clouds so stronger induced dipole-dipole forces. Boiling point is overcoming the intermolecular forces so stronger ones means a higher boiling point.

Question 38

How are permanent dipole-dipole interactions labelled?

Answer 38

With charges of delta+ and delta- on the atoms.

Question 39

When can hydrogen bonding occur?

Answer 39

When hydrogen is covalently bonded to fluorine, nitrogen or oxygen.

Question 40

Why are hydrogen bonds brought about?

Answer 40

Hydrogen has a high charge densiy and F, N and O are very electronegative. The bond is so polarised that a weak bond forms between the hydrogen of one molecule and a lone pair on a neighbouring molecule's F, N or O.

Question 41

What effect does hydrogen bonding have on a molecule?

Answer 41

Soluble in water. Higher boiling and freezing points than molecules of a similar size that don't form hydrogen bonds.

Question 42

What is an interesting property of ice caused by hydrogen bonding?

Answer 42

In ice, water molecules are held together in a lattice. When ice melts, hydrogen bonds are broken, so ice has more of these than water. As hydrogen bonds are long, this causes ice to be less dense than water.

Question 43

How do intermolecular forces explain simple covalent compounds having low melting and boiling points?

Answer 43

Weak intermolecular forces to overcome.

Question 44

How do intermolecular forces explain simple covalent compounds sometimes being soluble in water?

Answer 44

Water is also a polar molecule, hydrogen bonded molecules can form these with water molecules so are soluble.

Question 45

How do intermolecular forces explain simple covalent compounds not conducting electricity?

Answer 45

Overall covalent molecules are uncharged, permanent dipoles are not strong enough.

Question 46

what is the shape of molecules table?

Answer 46