Bonding (CDS)

Question 1

Describe the structure and bonding of atoms in a metal/alloy

Answer 1

Metal atoms are arranged in a regular lattice of cations surrounded by a sea of delocalised electrons

Question 2

What holds metal atoms in their fixed positions?

Answer 2

The metal is held together by the non-directional electrostatic attractions between the cations and the delocalised electrons

Question 3

Why do metals have high melting points?

Answer 3

Due to strong electrostatic attractions in their structure between cations and delocalised electrons

Question 4

Describe and explain the trend in melting points of metals as you go across a period

Answer 4

As you go across a period, the melting point of metals increases as the charge on the ions increase.

Question 5

Describe and explain the trend in melting points of metals as you go down a group

Answer 5

Down a group, melting points decrease because the shielding and atomic radius increases, so electrostatic forces of attraction between nuclei and delocalised electrons in the lattice are weaker.

Question 6

Why can metals conduct electricity?

Answer 6

Because they have delocalised electrons which are free to move and carry a charge

Question 7

Why can metals conduct heat?

Answer 7

Because delocalised electrons can absorb the heat energy and turn it into kinetic energy and move it around the structure of the metal.

Question 8

Why are metals malleable and ductile?

Answer 8

Due to the delocalised electrons, which can move as the lattice is distorted, maintaining the non-directional electrostatic attractions and therefore hold the metals shape.

Question 9

How are ions formed?

Answer 9

Ions are formed when electrons are transferred between elements that have a large difference in electronegativity

Question 10

What type of ions do metals form?

Answer 10

Positive

Question 11

What type of ions do non metals form?

Answer 11

Negative

Question 12

Describe the crystal structure of ionic compounds

Answer 12

A regular lattice of alternating cations and anions forms.

Question 13

What holds ions together in an ionic lattice?

Answer 13

Strong electrostatic forces between the ions

Question 14

Why do ionic compounds have high melting points?

Answer 14

Due to strong electrostatic attractions between positive and negative ions which require lots of energy to break.

Question 15

Why are ionic compounds soluble in water?

Answer 15

Water is very polar and can disrupt the electrostatic forces between ions and cause them to dissociate.

Question 16

Why are ionic compounds electrical insulators when solid?

Answer 16

Because ions are fixed in position, and they cannot carry a charge.

Question 17

Why are ionic compounds electrical conductors when molten or dissolved?

Answer 17

Ions are free to move around and carry a charge

Question 18

Why are ionic compounds brittle?

Answer 18

When hit, alternating arrangement of ions is disrupted, so they repel each other and the lattice breaks apart.

Question 19

What is a covalent bond?

Answer 19

A pair of shared electrons with opposite spin

Question 20

What type of elements do covalent bonds form between?

Answer 20

Elements with high electronegativity (non-metals)

Question 21

What are the forces of attraction involved in covalent bonds?

Answer 21

Electrostatic forces of attraction between the shared pair of electrons and the nuclei

Question 22

What are the two types of electron pair in covalently bonded molecules?

Answer 22

Bonding pairs and lone pairs

Question 23

How are covalent bonds represented?

Answer 23

With a line

Question 24

What is a dative covalent bond/co-ordinate bond?

Answer 24

A covalent bond in which both shared electrons are donated by the same atom

Question 25

How are co-ordinate bonds represented?

Answer 25

With an arrow pointing to the atom that is receiving the two electrons

Question 26

Order these pairs in order of least to most repulsion: Lone Pair - Lone Pair Bonding Pair - Bonding Pair Lone Pair - Bonding Pair

Answer 26

Least: BP - BP LP - BP Most: LP - LP

Question 27

Bond angles in a linear molecule

Answer 27

180

Question 28

Bond angles in a bent molecule

Answer 28

104.5

Question 29

Bond angles in a trigonal planar

Answer 29

120

Question 30

Bond angles in a tetrahedral molecule

Answer 30

109.5

Question 31

Bond angles in a trigonal pyramid

Answer 31

107

Question 32

Bond angles in a trigonal bipyramid

Answer 32

120 and 90

Question 33

Bond angles in a octahedral molecule

Answer 33

90

Question 34

Bond angles in a square pyramid

Answer 34

90

Question 35

Bond angles in a square planar

Answer 35

90

Question 36

What is electronegativity?

Answer 36

A measure of the power of an atom to attract a bonding pair of electrons.

Question 37

What are the three most electronegative elements?

Answer 37

Nitrogen, Oxygen, Fluorine

Question 38

What are the three intermolecular forces from weakest to strongest

Answer 38

Van Der Waals Permanent Dipole Hydrogen bonding

Question 39

How and why do Van Der Waals forces vary with the size/ Mr of molecules?

Answer 39

They get stronger as molecules get bigger as there are more electrons

Question 40

How are Van der Waals forces induced?

Answer 40

An instantaneous dipole in one molecule induces a dipole in another molecule and this induces a force of attraction between them.

Question 41

Which type of molecules ONLY have Van Der Waals forces?

Answer 41

Monatomic elements Diatomic Elements Large non-polar molecules

Question 42

True or False: All atoms and molecules have Van der Waals forces

Answer 42

True

Question 43

What are permanent dipole forces?

Answer 43

Electrostatic forces of attraction between the dipoles of two polar molecules

Question 44

What effect do permanent dipole forces have on the properties of a molecule

Answer 44

Greater melting and boiling point than expected due to energy required to break the stronger permanent dipole forces.

Question 45

What is hydrogen bonding?

Answer 45

A type of permanent dipole force that occurs when hydrogen is bonded to a Nitrogen, Fluorine or Oxygen

Question 46

Why is hydrogen bonding so much stronger than other permanent dipole forces?

Answer 46

N, O and F are the most electronegative elements so they create a very strong dipole.

Question 47

What effect does hydrogen bonding have on the properties of a molecule?

Answer 47

Much higher melting and boiling points than expected

Question 48

Why is ice less dense than water?

Answer 48

The orientation of hydrogen bonds causes molecules to push farther apart when frozen, which lowers the density.

Question 49

Describe the structure of Ice

Answer 49

Ice has a 3D hexagonal crystal structure

Question 50

What happens to solid iodine when it reaches its melting point?

Answer 50

It sublimes

Question 51

Why is iodines melting point so low?

Answer 51

Because it only has weak VdW forces which are easily broken.

Question 52

Describe the structure and bonding of diamond

Answer 52

Diamond has a tetrahedral structure. Each C makes 4 bonds with other carbons and they have a bond angle of 109.5 between them

Question 53

Why is diamond hard?

Answer 53

Diamond is really hard due to its structure and the strong C – C covalent bonds

Question 54

Why does diamond have a high melting point?

Answer 54

It has a very high melting point due to the strong C – C bonds which require lots of energy to break

Question 55

Why doesn't diamond conduct electricity?

Answer 55

All electrons are in a covalent bond so there is none available to move and carry a charge

Question 56

Why isn't diamond soluble in water?

Answer 56

Insoluble due to strong C – C bond

Question 57

Describe the structure and bonding of graphite

Answer 57

- Hexagonal arrangement. - Each C makes 3 bonds with other carbons, leaving a fourth delocalised valence electron for every carbon. - Weak VdW forces hold the layers of graphite together. - Bond angles between C is 120

Question 58

Why does graphite have a high melting point?

Answer 58

Strong C – C bond require lots of energy to break

Question 59

Why is graphite a conductor of electricity?

Answer 59

Due to delocalised electrons that are free to move and carry charge.

Question 60

Why is graphite soft?

Answer 60

Easily broken VdW forces hold the layers together, so they can easily slide over each other making it soft

Question 61

Why isn't graphite soluble in water?

Answer 61

It is insoluble due to strong C – C bonds