2a) Bonding and Calculations

Question 0

What does the atomic number tell us?

Answer 0

Number of protons

Question 1

What does the mass number tell us?

Answer 1

Total no. Of protons and neutrons

Question 2

What is the mass of each particle in an atom?

Answer 2

Proton: 1
Neutron: 1
Electron: very small

Question 3

How are compounds formed?

Answer 3

When atoms of two or more different elements combine together

Question 4

Define the term isotope

Answer 4

Different atomic forms of the same element which have the same number of protons but different number of neutrons

Same atomic number
Different mass number

Question 5

What is ionic bonding?

Answer 5

Atoms lose or gain electrons to form charged particles (called ions) which are strongly attracted to each other

Question 6

What kind of structure do ionic compounds have?

Answer 6

Giant ionic lattices

Ions forms a closely packed regular lattice arrangement

Question 7

Give an example of an ionic compound

Answer 7

Sodium chloride (salt)

Question 8

Why do ionic compounds have high melting and boiling points?

Answer 8

Giant ionic lattice structure
Strong electrostatic forces of attraction between ions
Takes large amount of energy to break forces

Question 9

When can ionic compounds carry electric current and why?

Answer 9

If molten or dissolved in water
Ions separate out and are free to move
Can easily carry electric current

Question 10

What is an ion?

Answer 10

An atom that has lost or gained an electron

Question 11

What is the overall charge of any compound?

Answer 11

Zero / neutral

Question 12

What is a covalent bond?

Answer 12

When atoms share electrons

Question 13

What are the two types of covalent substances?

Answer 13

Simple molecular substances

Giant covalent structures or macromolecules

Question 14

Describe simple molecular substances

Answer 14

Very strong covalent bonds
Weak forces of attraction (feeble intermolecular forces)
Very low melting and boiling points
Most gases or liquids at room temp.
Don’t conduct electricity - no ions - no electrical charge

Question 15

Describe macromolecules

Answer 15

All atoms have strong covalent bonds
No charge ions - don’t conduct electricity even when molten (except graphite)
Very high melting and boiling points

Question 16

Why is graphite the only non metal to conduct heat and electricity?

Answer 16

Each carbon atom had one delocalised (free) electron

Question 17

Why are metals good conductors of heat and electricity?

Answer 17

Delocalised (free) electrons - from outer shell of every metal atom
free to move through the structure

Question 18

Why can metals easily be bent or shaped?

Answer 18

Layers of atoms can slide over each other

Question 19

What is an alloy?

Answer 19

Mixture of two or more metals together

Question 20

Why are alloy harder than pure metals?

Answer 20

Different sized atoms due to mixture of different elements

Atoms distort the layers making it more difficult for them to slide past each other

Question 21

What is the difference between a giant ionic structure and a giant metallic structure?

Answer 21

Giant ionic - only conduct electricity when molten or dissolved in water, low melting and boiling points
Giant metallic - free electrons can always conduct electricity

Question 22

What determines the properties of plastics?

Answer 22

Intermolecular forces

Question 23

Describe thermosoftening polymers

Answer 23

Strong covalent bonds
Tangled chains of polymers
Weak intermolecular forces
Free to slide over each other
No cross links between chains
Easy to melt
When cools hardens to new shapes
Can be remoulded

Question 24

Describe thermosetting polymers

Answer 24

``` Strong covalent bonds Strong intermolecular forces called cross links between polymers Solid structure Doesn't soften when heated Strong, hard, rigid ```

Question 25

Compare how a low density and high density polythene is made

Answer 25

Low density polythene (flexible) - heating ethane at 200 degrees Celsius under high pressure High density polythene (rigid) - lower temperature, low pressure, catalyst

Question 26

What is relative atomic mass?

Answer 26

How heavy different atoms are compared to the mass of an atom of carbon-12 Same as mass number of the element

Question 27

What is relative formula mass?

Answer 27

All the relative atomic masses added together

Question 28

How do you convert between moles and grams

Answer 28

No. Of moles = mass in g/ relative atomic mass

Question 29

How do you calculate percentage yield?

Answer 29

Percentage yield = actual yield/predicted yield x 100

Question 30

What is a reversible reaction?

Answer 30

Where the products of the reaction can themselves react to produce the original reactants

Question 31

How can artificial colours be separated?

Answer 31

Using paper chromatography

Question 32

What is retention time?

Answer 32

The time different gases travelling at different speeds take to reach the detector in gas chromatography

Question 33

What is the yield of a reaction?

Answer 33

Mass of product

Question 34

How do you work out percentage mass of an element in a compound?

Answer 34

(Relative atomic mass x no. of element atoms / Relative formula mass of compound) x 100

Question 35

What is the empirical formula?

Answer 35

Experimental mass of element/ atomic mass of element , convert to ratio

Question 36

How do you work out the number of moles?

Answer 36

Mass/relative formula mass

Question 37

How do you work out percentage yield?

Answer 37

Actual yield / predicted yield x 100

Question 38

What does a molecular ion peak reveal about a molecule?

Answer 38

Its relative molecular mass