Bonding And Structure

Question 1

Do ionic compounds dissolve in polar solvents?

Answer 1

Yes

Question 2

Why do ionic compounds dissolve/do not dissolve in polar solvents?

Answer 2

The polar water molecules break down the lattice by surrounding each ion to form a solution

Question 3

What shape is the molecule if it has 2 bonding pairs?

Answer 3

Linear

Question 4

What shape is the molecule if it has 3 bonding pairs?

Answer 4

Trigonal planar

Question 5

What shape is the molecule if it has 4 bonding pairs?

Answer 5

Tetrahedral

Question 6

What shape is the molecule if it has 3 bonding pairs and 1 lone pair?

Answer 6

Trigonal pyramidal

Question 7

What shape is the molecule if it has 2 bonding pairs and 2 lone pairs?

Answer 7

Non-linear

Question 8

What shape is the molecule if it has 5 bonding pairs?

Answer 8

Trigonal bipyramidal

Question 9

What shape is the molecule if it has 6 bonding pairs?

Answer 9

Octahedral

Question 10

What are the bond angles in a linear molecule?

Answer 10

180

Question 11

What are the bond angles in a trigonal planar molecule?

Answer 11

120

Question 12

What are the bond angles in a tetrahedral molecule?

Answer 12

109.5

Question 13

What are the bond angles in a trigonal pyramidal molecule?

Answer 13

107

Question 14

What are the bond angles in a non-linear molecule?

Answer 14

104.5

Question 15

What are the bond angles in a trigonal bipyramidal molecule?

Answer 15

90,120 and 180

Question 16

What are the bond angles in an octahedral molecule?

Answer 16

90 and 180

Question 17

What is a giant ionic lattice?

Answer 17

A 3D structure of oppositely charged ions held together by strong ionic bonds

Question 18

What is electronegativity?

Answer 18

A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond

Question 19

What is a permanent dipole?

Answer 19

A small charge different across a bond that results from a difference in the electronegativities of the bonded atoms

Question 20

What does a polar covalent bond have?

Answer 20

A permanent dipole

Question 21

What does a polar molecule have?

Answer 21

An overall dipole when you take into account any dipoles across the bonds

Question 22

What is an intermolecular force?

Answer 22

An attractive force between neighbouring molecules

Question 23

What is a permanent dipole-dipole force?

Answer 23

A weak attractive force between permanent dipoles in neighbouring molecules

Question 24

What are van der Waals’ forces?

Answer 24

Attractive forces between induced dipoles in neighbouring molecules

Question 25

What is a hydrogen bond?

Answer 25

A strong dipole-dipole attraction between an electron deficient H atom on one molecule and a lone pair of electrons on a highly electronegative atom on a different molecule

Question 26

What are delocalised electrons?

Answer 26

Electrons shared between more than 2 atoms

Question 27

What is a giant metallic lattice?

Answer 27

A 3D structure of positive ions and delocalised electrons bonded together by strong metallic bonds

Question 28

What is a simple molecular lattice?

Answer 28

A 3D structure of molecules bonded together by weak intermolecular forces

Question 29

What is a giant covalent lattice?

Answer 29

A 3D structure of atoms bonded together by strong covalent bonds

Question 30

What are Id-Id or London forces?

Answer 30

Forces that exist between all simple molecules

Question 31

How are Id-Id or London forces created?

Answer 31

1) Electrons are randomly moving within the electron shells of a molecule
2) This can cause electron density to be spread unevenly, causing an instantaneous dipole
3) If a second molecule approaches, a small induced dipole occurs causing a weak attraction between the 2 molecules
4) This weak attraction is known as an induced dipole-dipole interaction or London forces

Question 32

Which forces can explain the trend of boiling points of the noble gases?

Answer 32

London forces

Question 33

Explain the trend of boiling points of the noble gases

Answer 33

Going down the group, the number of electrons per atom increases and this increases the strength of the London forces (larger electron density and thus bigger dipoles) so more energy is needed to overcome the London forces and allow the substance to boil

Question 34

Outline polar molecules

Answer 34

They have permanent dipoles due to the much greater electronegativity of one of the atoms. Hence the oppositely charged ends of 2 molecules are attracted which is called a permanent dipole-dipole interaction

Question 35

What are Pd-Pd and Id-Id forces known as?

Answer 35

van der Waals’ forces

Question 36

What 3 conditions must there be for a hydrogen bond to form?

Answer 36

A hydrogen atom
A lone pair
On oxygen, nitrogen or fluorine

Question 37

Outline the density of ice

Answer 37

Unusual as ice less than liquid
Hydrogen bonds in open lattice keep molecules apart to a greater extent than in water
As it melts, some hydrogen bonds break, allowing water molecules to pack more closely to each other, increasing density

Question 38

Outline simple molecules

Answer 38

Many covalently bonded molecules form simple molecular lattices - strong covalent bonds between atoms within molecule but weak intermolecular forces

Question 39

Outline the 3 properties of simple molecules

Answer 39

Low melting and boiling points due to weak intermolecular forces
Does not conduct electricity as no free electrons or free ions to carry charge
Dissolve in solvents with intermolecular forces of similar strength

Question 40

Why can covalent bonds of the same type have different strengths?

Answer 40

The environments of the bonds vary

Question 41

What is the average bond enthalpy?

Answer 41

The average amount of energy needed to break one mole of a bond