Bonding and structure- bonding

Question 1

What is meant by the term ionic bond?

Answer 1

The electrostatic attraction between positively and negatively charged ions

Question 2

What is meant by the term covalent bond?

Answer 2

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

Question 3

What is a molecule?

Answer 3

A small group of atoms bonded together by covalent bonds

Question 4

What are lone pairs?

Answer 4

A pair of electrons in the outer shell NOT used in conding

Question 5

What is a dative covalent bond?

Answer 5

A shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only

Question 6

Why do metals have high melting and boiling points?

Answer 6

• Strong electrostatic attraction between metal cations and delocalised electrons
• Requires a lot of energy to break

Question 7

Why are metals good electrical conductors when solid?

Answer 7

-Delocalised electrons can move and carry charge

Question 8

Why are metals good electrical conductors when molten?

Answer 8

-Delocalised electrons and metal cations can move and carry charge

Question 9

Why are metals insoluble in water?

Answer 9

• strong electrostatic attraction between metal cations and delocalised electrons which require a lot of energy to break
• This energy is not avaliable

Question 10

Why do the melting points of metals increase in order from sodium, magnesium, aluminium?

Answer 10

• the charge on the metal ion increases from 1+, to 2
  +, to 3+
  -the no. delocalised electrons per ion increases
  -this results in a stronger electrostatic attraction between metal ions and delocalised electrons
  -more energy is necessary to break them

Question 11

Out of sodium, magnesium, and aluminium which would you expect to be the best conductor of electricity and why?

Answer 11

Aluminium

• greatest no. delocalised electrons per metal ion
• greatest capacity for carrying charge

Question 12

How does the model of metallic bonding explain why metals are ductile and malleable?

Answer 12

-layers of ions can slide over each other easily

Question 13

What metals are present in the following alloys?

i) Brass
ii) Stainless steel

Answer 13

i) Zinc and Copper

ii) Iron and Chromium

Question 14

How does an alloy make a metal harder?

Answer 14

• Each metal ion is a slightly different size

- So layers of ions do not slide over each other so easily

Question 15

What does ductile mean?

Answer 15

Able to be drawn into a wire

Question 16

Define ion

Answer 16

A positively or negatively charged atom or (covalently bonded) group of atoms where the number of protons differs from the number of electrons

Question 17

Define giant ionic lattice

Answer 17

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

Question 18

Define simple molecular lattice

Answer 18

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

Question 19

Define giant covalent lattice

Answer 19

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

Question 20

Define giant metallic lattice

Answer 20

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

Question 21

Why do ionic substances have high melting and boiling points?

Answer 21

• strong electrostatic attractions between anions and cations
• require a lot of energy to overcome

Question 22

Why are ionic substances non-conductors of electricity when solid?

Answer 22

• the ions are fixed in the lattice

- so cannot move and carry charge

Question 23

Why are ionic substances good electrical conductors when in solution or molten?

Answer 23

• the ions are no longer fixed in the lattice

- and so are free to move and carry charge

Question 24

Why do ionic substances generally have good solubility in water?

Answer 24

• oxygen atoms in water are attracted to and surround the positive ions
• hydrogen atoms in water are attracted to and surround the negative ions
• this results in the breaking down of the ionic lattice and the compound dissolving

Question 25

Why are ionic substances brittle?

Answer 25

- slight movement of the layer of ions bring positive ions next to positive ions and negative ions next to negative ions - this causes repulsion and the structure breaking apart

Question 26

What two factors affect the melting point of an ionic substance?

Answer 26

- IONIC radius | - Charge on the ions

Question 27

What are the boiling and melting points of simple molecular substances like? why?

Answer 27

Low | -because weak intermolecular forces between molecules require little energy to break

Question 28

Are simple molecular substances good electrical conductors? Why?

Answer 28

No | -they have no mobile charge carriers

Question 29

Are simple molecular substances soluble in non-polar solvents? Why?

Answer 29

Yes - solvent molecules are able to form similar intermolecular forces with molecules - weak intermolecular forces do not need much energy to overcome

Question 30

What are the boiling and melting points of giant covalent substances like? why?

Answer 30

High | -strong electrostatic attractions must be overcome which requires a lot of energy

Question 31

Are giant covalent substances good electrical conductors? Why?

Answer 31

No | -they do not contain and free mobile charge carriers

Question 32

Are giant covalent substances soluble in non-polar solvents? Why?

Answer 32

No | -strong covalent bonds between atoms require too much energy to be overcome

Question 33

Can diamond conduct electricity? Why?

Answer 33

No | Contains no mobile charge carriers

Question 34

Can graphite conduct electricity? Why?

Answer 34

Yes | -contains delocalised electrons in layers which are free to move and carry charge

Question 35

How hard is diamond? Why?

Answer 35

Very hard - tetrahedral structure of atoms means forces are spread through the structure - strong covalent bonds require a lot of energy to be broken

Question 36

How hard is graphite? Why?

Answer 36

Soft - weak intermolecular forces require little energy to overcome and so can be easily broken - layers can slide over each other

Question 37

Are simple molecular substances often soluble in water?

Answer 37

Yes