Structure and Bonding

Question 1

Compound

Answer 1

A substance with two or more elements chemically bonded

Question 2

Chemical bond

Answer 2

Involves either transferring (losing or gaining) OR sharing electrons in the highest occupied energy levels (shells) of atoms in order to achieve the electronic structure of a noble gas.

Question 3

Element

Answer 3

A substance that is made from one type of particle – named on the periodic table.

Question 4

Mixture

Answer 4

A substance with two or more elements that is not chemically bonded and therefore can be separated.

Question 5

Giant Covalent Structure

Answer 5

Made of only non-metal elements

Each atom is joined to adjacent atoms by covalent bonds.

The atoms are usually arranged into giant regular lattice.

Examples: Graphite, Diamond, Silicon dioxide

Question 6

Describe Graphite

Answer 6

Each carbon atom forms three covalent bonds.

Sheet of carbon atoms are arranged into layer.

Question 7

Properties of Graphite

Answer 7

Used for pencils and as a lubricant.

High melting point:

Conducts:

insolubility/does not dissolve

Question 8

Explain why Graphite can be used for pencils and lubricants.

Answer 8

Layers can slide over each other therefore can be used for pencils and as a lubricant

Question 9

Explain the melting point of Graphite

Answer 9

High melting point: -

3 strong covalent bonds need to be broken

therefore requires lots of energy to break these covalent bonds.

Question 10

Explain why Graphite can conduct electricity

Answer 10

Conducts because each carbon has an electron that is free (or delocalised)

so can move through the whole structure.

Question 11

Explain the solubility of graphite

Answer 11

Not soluble as water cannot separate the layers or atoms

Question 12

Describe the bonding of diamond

Answer 12

Each carbon atom forms 4 covalent bonds to 4 carbon atoms

in an extended lattice structure

resulting in a rigid structure.

Question 13

Properties of Diamond

Answer 13

High melting point:

Does not conduct

insoluble/not soluble

Question 14

Explain the melting point of diamond

Answer 14

4 strong covalent bonds need to be broken

therefore requires lots of energy to break to these covalent bonds

Question 15

Explain the conductivity of diamond

Answer 15

Does not conducts

because no electrons

to transfer charge through whole of the structure.

as the electrons are in covalent bonds

Question 16

Explain the solubility of diamond

Answer 16

Insoluble/Not soluble

as water cannot separate the carbon atoms

Question 17

Describe the bonding of silicon dioxide

Answer 17

Each silicon forms covalent bonds to 4 oxygen atoms and each oxygen forms 2 covalent bonds to silicon atoms,

which results in a rigid lattice structure.

Question 18

Properties of silicon dioxide

Answer 18

High melting point

Does not conducts

insoluble/not soluble

Question 19

Explain the melting point of Silicon dioxide

Answer 19

High melting point:

Each silicon has 4 strong covalent bonds need to be broken

therefore requires lots of energy to break.

Question 20

Explain the conductivity of silicon dioxide

Answer 20

Does not conducts

because no electrons

to transfer charge through whole of the structure.

as the electrons are in covalent bonds

Question 21

Explain the solubility of silicon dioxide

Answer 21

insoluble /not soluble

as water cannot separate the carbon atoms

Question 22

Covalent bond

Answer 22

Chemical bond that involves the sharing of electron pairs between atoms.

Question 23

Electron configuration

Answer 23

Description of how the electrons are arranged. E.g. 2, 8, 8 or Dot-cross diagrams.

Element have the same number of electrons in outer shell as it group number (Group 0 having a full shell)

Ions have a full outer shell of electrons

Question 24

Covalent compounds

Answer 24

Compounds formed between non-metal atoms.

Each bond consists of a shared pair of electrons, and is very strong.

Covalently bonded substances fall into two main types:

1. Simple covalent and
2. Giant covalent structures.

Question 25

Describe Simple covalent

Answer 25

Made of only non-metal elements only These contain only a few atoms held together by strong covalent bonds. usually small molecules like chlorine, bromine, iodine, water, ammonia, hydrogen, oxygen, nitrogen, etc

Question 26

Properties of simple covalent compounds

Answer 26

Low melting points: Does not conduct electricity

Question 27

Explain why simple covalent compounds have a low melting point.

Answer 27

Due to weak intermolecular bonds between molecules that do not require much energy to break.

Question 28

Explain why simple covalent compounds do not conduct electricity.

Answer 28

They do not have any free electrons or ions Hence no overall electric charge.

Question 29

Ions

Answer 29

Atoms that have lost electrons and are positively charged OR atoms that have gained electrons and are negatively charged.

Question 30

Ionic bond

Answer 30

Chemical bond that involves the electrostatic attraction of oppositely charged ion.

Question 31

Positive ion

Answer 31

Atoms that have lost electrons so have more protons than electrons.

Question 32

Negative ion

Answer 32

Atoms that have gained electrons so have more electrons than protons.

Question 33

Describe the Ionic lattice Structure

Answer 33

Made from Metal and non-metal ions Closely packed rows of alternating positive and negative ions:

Question 34

Properties of ionic compounds

Answer 34

High melting point: Conducts when dissolved and molten Does not conduct when solid

Question 35

Explain the melting point of ionic compounds.

Answer 35

High melting point Due to strong electrostatic attraction between oppositely charged ions that require a lot of energy to break.

Question 36

Explain the conductivity of ionic compounds when dissolved or molten.

Answer 36

Conducts electricity when dissolved and molten as the ions are free to move and transfer the charge.

Question 37

Explain the conductivity of ionic compounds when Solid

Answer 37

Does not conduct electricity ions are fixed in a lattice structure cannot transfer the charge.

Question 38

Metallic bond

Answer 38

Chemical bond that involves the electrostatic attraction between positive ion and delocalised electrons.

Question 39

Describe the Metallic lattice structure

Answer 39

Closely packed rows of positive ions and a sea of free/delocalised electrons

Question 40

Properties of Metals

Answer 40

High melting point Conducts Can be easily shaped or bend

Question 41

Explain the melting point of metals

Answer 41

High melting point: strong electrostatic attraction between positive metal ion and delocalised electrons which required lots of energy to break

Question 42

Explain why metals can conduct electricity

Answer 42

Due to the free delocalised electron that can move through the whole structure.

Question 43

Explain why metals can conduct heat

Answer 43

Due to the free delocalised electron that can move and transfer heat through the whole structure

Question 44

Explain why metals can be easily shaped or bend

Answer 44

because the positive ions arranged in layers which can easily slide over each other.

Question 45

Alloy

Answer 45

Made from two or more different metals.

Question 46

Explain why alloys are stronger than pure metals

Answer 46

Alloys have different sized ions in the metal distorts the layers (of positive ions) in the structure. making it more difficult for them to slide over each other.

Question 47

Memory Shape Alloys

Answer 47

Returns to their original shape after being deformed (reshaped) – usually by warming up the metal.

Question 48

Nitinol

Answer 48

Example of a memory shape metal used in braces for teeth