2.2.2 Bonding and structure

Question 1

Ionic bonding

Answer 1

Electrostatic attraction between positive and negative ions

Question 2

Giant ionic lattice

Answer 2

Results from oppositely charged ions strongly attracted in all directions

Question 3

Why do giant ionic lattices have high melting and boiling points

Answer 3

Electrostatic forces holding the ionic lattice together are strong and require a large amount of energy to overcome

Question 4

Describe electrical conductivity of ionic compounds in solid state

Answer 4

In the solid state, ions are in fixed positions with no mobile charge carriers, so the substance can’t conduct electricity

Question 5

Describe electrical conductivity of ionic compounds in molten or aqueous state

Answer 5

When molten or aqueous (in solution), ionic substances can conduct electricity as ions are mobile and no longer held in a lattice. They are free to move and carry a flow of charge.

Question 6

In what type of solvents do ionic lattices dissolve

Answer 6

Polar solvents e.g. water

Question 7

Covalent bonding

Answer 7

Strong electrostatic
attraction between a shared pair of electrons and
the nuclei of the bonded atoms

Question 8

Single covalent bond

Answer 8

Electrostatic attraction between one shared pair of electrons and the nuclei of two bonded atoms

Question 9

How many single covalent bonds does carbon make

Answer 9

4

Question 10

How many single covalent bonds does oxygen make

Answer 10

2

Question 11

How many single covalent bonds does hydrogen make

Answer 11

1

Question 12

Multiple covalent bond

Answer 12

Electrostatic attraction between more than one shared pair of electrons and the nuclei of two bonded atoms

Question 13

Dative covalent (coordinate) bond

Answer 13

A bond where both of the electrons in the shared pair are supplied from a single atom

(indicated using an arrow from the lone electron pair)

Question 14

Lone pair of electrons

Answer 14

Pairs of electrons not involved in bonding

Question 15

What are the types of covalent structure

Answer 15

-simple molecular lattice
-giant covalent lattice

Question 16

Describe the bonding in simple molecular structures

Answer 16

Atoms within the same molecule are held by strong covalent bonds and different molecules are held by weak intermolecular forces

Question 17

Why do simple molecular structures have low melting and boiling point

Answer 17

A small amount of energy is enough to overcome weak intermolecular forces

Question 18

Describe electrical conductivity of simple molecular structures

Answer 18

Non-conductors because no mobile charge carriers

Question 19

In what type of solvents do simple molecular structures dissolve

Answer 19

Non polar solvents

Question 20

Give three examples of giant covalent structures

Answer 20

-Diamond
-Graphits
-Silicon dioxide, SiO2

Question 21

Why do giant covalent structures have high melting and boiling points

Answer 21

Strong covalent bonds within the molecules need to be broken which require a large amount of energy to overcome

Question 22

List three properties of giant covalent structures

Answer 22

-High melting and boiling point
-Non conductors of electriity (except graphite)
-Insoluble in polar and non-polar solvents

Question 23

Describe bonding and structure in diamond

Answer 23

Each carbon atom forms 4 very strong covalent bonds with other carbons in a tetrahedral arrangement

Question 24

Why can graphite conduct electricity

Answer 24

Delocalised electrons present between the layers and move through the 2D lattice carrying electrical charge

Question 25

Metallic bonding

Answer 25

Electrostatic attraction between positively-charged metal ions and sea of negatively-charged delocalised electrons

Question 26

Why do giant metallic structures have high melting and boiling points

Answer 26

Strong metallic bonds need to be broken which requires a large amount of energy to overcome

Question 27

List three factors which affect strength of metallic bonds

Answer 27

-Number of delocalised electrons per atom -Charge of the metal cation -Radius of the metal cation

Question 28

How does number of delocalised electrons per atom affect strength of metallic bonds

Answer 28

-Metals with higher number of delocalised electrons per atom tend to form stronger metallic bonds -increased number of delocalised electrons allows for stronger electrostatic attractions between the electrons and the metal cations

Question 29

How does charge of the metal cation affect strength of metallic bonds

Answer 29

-A higher cation charge results in stronger electrostatic attractions between the cation and the delocalised electrons

Question 30

How does radius of the metal cation affect strength of metallic bonds

Answer 30

-Smaller metal cations have a higher charge density, which allows them to hold the delocalised electrons closer to the nucleus -This proximity enhances the electrostatic attractions between the cation and the electrons, resulting in a stronger metallic bond

Question 31

What does the shape of a simple molecule or ion depend on

Answer 31

Number of electron pairs around the central atom, and repulsion between them. Each electron pair naturally repels each other so that largest bond angle possible exists.

Question 32

By how many degrees does each lone pair reduce the bond angle

Answer 32

2.5°

Question 33

Electronegativity

Answer 33

The ability of an atom to attract the bonding electrons in a covalent bond towards itself

Question 34

In which direction of the periodic table does electronegativity increase

Answer 34

Top right, towards F

Question 35

Describe trends in electronegativity across a period

Answer 35

Increases -atomic radius decreases -charge density increases

Question 36

Describe trends in electronegativity down a group

Answer 36

Electronegativity decreases -electron shielding increases -atomic radius increases --so charge density decreases

Question 37

Permanent dipole

Answer 37

When there is a small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms