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Key Concepts Flashcards

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1
Q

How can chemical reactions be shown?

A

Using word equations or symbol equations

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2
Q

What do state symbols show?

A

The physical state of the reactants and products

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3
Q

What are compounds?

A

Combinations of atoms of different elements

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4
Q

What do symbol equations show?

A

Symbols or formulas of the reactants and products

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5
Q

Chemical formula for ammonia?

A

NH3

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6
Q

Chemical formula for ammonium

A

NH4+

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7
Q

Chemical formula for nitrate

A

NO3-

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8
Q

Chemical formula for hydroxide

A

OH-

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9
Q

Chemical formula for carbonate

A

2-

CO3

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10
Q

Chemical formula for sulfate

A

2-

SO4

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11
Q

How do ions form?

A

When atoms, or groups of atom, gain or lose electrons to form charged particles

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12
Q

Hazard

A

Anything with the potential to cause harm or damage

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13
Q

What are atoms?

A

Tiny particles of matter which make up everything

The smallest pieces of an element

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14
Q

How did John Dalton describe atoms at the start of the 19th century?

A

Solid spheres that cannot be split

Different spheres made up the different elements

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15
Q

Who concluded that atoms weren’t solid spheres? What did he discover?

A

JJ Thomson in 1897

He discovered electrons

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16
Q

What did JJ Thomson conclude from his experiments on atoms?

A

Atoms weren’t solid spheres that cannot be divided

Atoms have an internal structure

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17
Q

How did JJ Thompson show atoms have an internal structure?

A

His measurements of charge and mass showed an atom must contain even smaller, negatively charged particles- electrons

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18
Q

What did JJ Thomson change the ‘solid sphere’ idea of atomic structure to?

A

The plum pudding model

A ball of positive charge with negatively charged electrons mixed in

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19
Q

What proved the plum pudding model wrong?

A

The gold foil experiment in 1909 by Ernest Rutherford

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20
Q

What was the gold foil experiment?

A

Firing positively charged alpha particles at a thin sheet of gold

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21
Q

What were they expecting to see during the gold foil experiment because of the plum pudding model?

A

The particles to pass through the sheet or be slightly deflected because the positive charge of each atom was thought to be very spread out through the ‘pudding’ of the atom

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22
Q

What happened during the gold foil experiment?

A

Most alpha particles went through the gold sheet, some were deflected more than expected, and a small number were deflected backward

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23
Q

In the alpha particle experiment, what did some particles bouncing back tell the scientists?

A

The centre of the atom must contain a lot of mass- we call this the nucleus

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24
Q

In the alpha particle experiment, what did most particles passing through tell the scientists?

A

Atoms are mainly just empty space

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25
Q

In the alpha particle experiment, what did some particles getting deflected tell the scientists?

A

The centre of the atom must have a positive charge

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26
Q

What theory did Rutherford come up with after the gold foil experiment?

A

The theory of the nuclear atom
In this there’s a tiny, positively charged nucleus at the centre, surrounded by a ‘cloud’ of negative electrons
Most of the atoms empty space

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27
Q

What did scientists realise about Rutherford’s idea of electrons in a cloud?

A

The electrons would be attracted to the nucleus, causing the atom to collapse

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28
Q

What did Niels Bohr propose?

A

A new model of the atom where all the electrons were contained in shells
He suggested the electrons only existed in shells and each shell has a fixed energy

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29
Q

What did James Chadwick discover in 1932?

A

Neutrons

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30
Q

What are atoms made up of?

A

3 subatomic particles:
Protons- heavy and positively charged
Neutrons- heavy and neutral
Electrons- hardly any mass and negatively charged

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31
Q

Characteristics of the nucleus

A 
Middle of the atom
Protons and neutrons 
Positive charge due to protons 
Almost whole mass of atom concentrated here 
Tiny compared to overall size of atom
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32
Q

Characteristics of electrons

A 
Move around nucleus in shells
Negatively charged 
Tiny but shells cover a lot of space 
Size of shells determines size of atom
                               -10
Radius of about 10    m
Tiny mass
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33
Q

Why are atoms neutral?

A

They have the same amount of protons and electrons

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34
Q

What does the nuclear symbol of an atom tell us?

A

It’s atomic (proton) number and mass number

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35
Q

What does the mass number tell us?

A

Total number of protons and neutrons

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36
Q

Isotopes

A

Different forms of the same element
Same number of protons, different number of neutrons
Same atomic number, different mass number

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37
Q

Relative atomic mass

A

The average mass of one atom of the element, compared to half the mass of one atom or carbon-12

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38
Q

Why might the relative atomic mass not be a whole number?

A

It is the average of the mass numbers of all the different isotopes of an element, taking into a count their abundance

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39
Q

How to find out relative atomic mass

A

Multiply each relative isotopic mass by its isotopic abundance and add up the results
Divide the sum by its abundances

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40
Q

Differences between the modern periodic table and Mendeleev’s

A

Modern- element ordered in atomic number, Mendeleev- protons hadn’t been discovered so ordered them by atomic mass
Modern- has noble gases, Mendeleev- left gaps for undiscovered elements

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41
Q

Who made the first proper periodic table?

A

Dimitri Mendeleev in 1869

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42
Q

How many elements did Mendeleev arrange?

A

50

43
Q

How did Mendeleev order the elements?

A

He sorted them into groups, based on properties and the properties of their compounds
Ordered them in order of relative atomic mass so he could put elements with similar chemical properties in columns

44
Q

Why was the atomic mass Mendeleev had sometimes wrong?

A

The presence of isotopes

45
Q

What did Mendeleev do when some elements didn’t fit the pattern of similar chemical properties being in columns?

A

He switched the order of the elements to keep those with the same properties in the same columns

46
Q

What did Mendeleev also have to do to keep elements with the same properties together?

A

Left gaps for undiscovered elements
Used properties of other elements in the column to predict their properties
They were found and matched his pattern, confirming his ideas

47
Q

Why did Mendeleev order his table by atomic mass?

A

Protons hadn’t been discovered

48
Q

What are elements on the modern periodic table ordered by?

A

Ascending atomic number

They fit the patterns Mendeleev worked out

49
Q

How is the modern periodic table laid out?

A

In columns called groups where elements with similar chemical properties are together

50
Q

What determines which column the element belong to on the periodic table?

A

The number of electrons in its outer shell

51
Q

What are rows called?

A

Periods

Each period represents another full shell of electrons

52
Q

What corresponds to the period an element belongs to?

A

The number of shells of electrons an element has

53
Q

What are 3 electron shell rules?

A

They always occupy shells
Lowest energy levels are always filled first
Only a certain number of electrons are allowed in each shell (1st= 2, 2nd= 8, 3rd= 8

54
Q

What does the group number tell us?

A

How many electrons occupy the outer shell of the element

55
Q

Ions

A

Charged particles- they can be single atoms or groups of atoms

56
Q

Why do atoms lose or gain electrons?

A

To gain a full outer energy level

To gain a stable electronic structure

57
Q

Anions

A

Negative ions that form when atoms gain electrons

More electrons than protons

58
Q

Cations

A

Positive ions
Form when atoms lose electrons
More protons than electrons

59
Q

Which groups are most likely to form ions?

A

1,2,6,7

60
Q

Which groups lose electrons?

A

1,2
Metals
Form cations

61
Q

Which groups gain electrons?

A

6 and 7
Non metals
Form anions

62
Q

Why do elements in the same group all form ions with the same charges?

A

They all have the same number of outer electrons

They have to lose or gain the same number to achieve a full outer shell

63
Q

What are ionic compounds made up of?

A

A positively charged part and a negatively charged part

64
Q

What is the overall charge of any ionic compound?

A

0

Positive charges must balance negative ones

65
Q

What are the three types of bonding?

A

Ionic
Covalent
Metallic

66
Q

What is an ionic bond?

A

The transfer of electrons between a metal and a non metal. The metal loses electrons and becomes a cation, the non metal gains electrons to form and anion. These oppositely charged ions are strongly attracted to one another by electrostatic forces

67
Q

What do dot and cross diagrams show?

A

How ionic compounds form

Show the arrangement of electrons in an atom or ion

68
Q

What structure do ionic compounds have?

A

Giant lattice- very strong electrostatic forces of attraction between oppositely charged ions

69
Q

Properties of ionic compounds

A

High melting and boiling points due to strong attraction between ions- lots of energy needed to overcome this
Solid ionic compounds don’t conduct electricity because the ions are fixed in place and cannot move
Liquid ionic compounds carry an electric current because the electrons are free to move
Soluble in water because ions separate and are free to move in the solution, they’ll carry an electric current

70
Q

2D representations advantages and disadvantages

A 
Simple 
Show what atoms something contains 
Shows how atoms connect
Don’t show shape or substance 
No idea about size
71
Q

Dot and cross diagram advantages and disadvantages

A

Show how compounds or molecules are formed
Show where electrons in bonds or ions came from
Don’t show size or arrangement of atoms or ions

72
Q

3D models advantages and disadvantages

A

Show arrangement of ions

Only show outer layer

73
Q

Ball and stick model advantages and disadvantages

A 
Visual 
Show shape of lattice or molecule in 3D
More realistic than 2D
Show gaps between atoms- misleading 
Don’t show correct scales of atoms or ions
74
Q

Covalent bond

A

A strong bond that forms when a pair of electrons is shared between 2 atoms

75
Q

What are simple molecular substances made from?

A

Molecules containing a few atoms joined by covalent bonds

76
Q

Properties of simple molecular substances

A

Atoms within molecules held together by strong covalent bonds
Forces of attraction between molecules are weak
Low melting and boiling points because the intermolecular forces are feeble and easily broken
Gases or liquids at room temperature
As they get bigger, strength of intermolecular forces increases and melting and boiling points increase
Don’t conduct electricity because they don’t contain free electrons or ions
Some soluble and some aren’t

77
Q

What are polymers?

A

Molecules made of long chains of covalently bonded carbon toms
Eg polyethene
Form when small molecules called monomers join together

78
Q

Properties of giant covalent structures

A

All atoms bonded by strong covalent bonds
High melting and boiling points
Usually don’t conduct electricity (apart from graphite and graphene) as they normally don’t contain charged particles
Aren’t water soluble

79
Q

Examples of carbon based giant covalent structures

A

Diamond
Graphite
Graphene

80
Q

Diamond properties

A

Made of a network of carbons that each form 4 covalent bonds
Strong covalent bonds- high melting point
Strong covalent bonds hold atoms in a rigid lattice structure making it really hard. Used to strengthen cutting tools
Doesn’t conduct electricity as it has no free electrons or ions

81
Q

Graphite properties

A

Each carbon atom forms 3 covalent bonds creating sheets of carbon atoms arranged in hexagons
No covalent bonds between layers- held together weakly so move over each other making graphite soft and slippery. Used as a lubricating material
High melting point as covalent bonds in layers need loads of energy to break
1 out of each carbons 4 outer electrons used in bonds do each carbon atom has one electron delocalised and can move. Therefore graphite conducts electricity and is often used to make electrodes

82
Q

Graphene properties

A 
A fullerene 
One layer of graphite 
Sheet of carbon atoms joined together in hexagons 
One atom thick
2d compound
83
Q

Fullerenes

A

Molecules of carbon shaped like closed tubes or hollow balls

84
Q

Properties of fullerenes

A

Made up of carbon atoms arranged in hexagons but also contain pentagons or heptagons
Cage other molecules- could be used to deliver a drug directly to cells in the body
Huge surface area so could help make industrial catalysts

85
Q

What are nanotubes?

A

Fullerenes
Tiny cylinders of graphene- conduct electricity
High tensile strength so can strengthen materials without adding weight
Used in sports equipment

86
Q

Example of a fullerene

A 
Buckminsterfullerene 
C60
Forms a hollow sphere made of 20 hexagons and 12 pentagons 
Stable molecule
Forms soft brownish black crystals
87
Q

Metallic bonding

A

Forces of electrostatic attraction between positive metal ions and shared negative electrons that hold the atoms together in a regular lattice

88
Q

What does metallic bonding involve?

A

Delocalised electrons in the outer shell of metal atoms

89
Q

Physical properties of metals

A

Very strong electrostatic forces between metal ions and delocalised seas of electrons
High melting and boiling points due to this- shiny solids at room temperature
Not water soluble
Denser than non metals as ions in metallic structure are packed closely together
Malleable- layers of atoms can slide over each other
Conduct heat and electricity- delocalised electrons carry an electric current and thermal heat energy through the material

90
Q

Why do metals have similar basic physical properties?

A

They all have metallic bonding

91
Q

Why don’t non metals have the same properties as metals?

A

They don’t have metallic bonding

92
Q

Why do non metals have a variety of chemical and physical properties?

A

They form a variety of different structures

93
Q

Properties of non metals

A 
Dull looking 
Brittle 
Lower boiling points- not solids at room temp
Don’t conduct electricity 
Lower density
94
Q

How do non metals and metals have different chemical properties?

A

Non metals gain electrons to form full outer shells

Metals lose electrons to gain full outer shells

95
Q

Why is mass always conserved in a chemical reaction?

A

No atoms are destroyed or created
There are the same number and type of atoms on each side of a reaction equation
Total mass of the system before and after doesn’t change

96
Q

What is a precipitation reaction?

A

When two solutions react and an insoluble solid- called a precipitate- forms in the solution

97
Q

How can we show conservation of mass?

A

Precipitation reaction

98
Q

What is usually involved if the mass changes in an experiment?

A

A gas

99
Q

Why might mass increase in an unsealed reaction vessel during a reaction?

A

If it increases its probably because at least one of the reactants is a gas found in air and the products are solids liquids or aqueous.
Before reaction gas is floating in air, its not contained in the reaction vessel so you can’t measure its mass
When gas reacts to form part of the product, it becomes contained inside the reaction vessel
Total mass inside reaction vessel increases

100
Q

Why might mass decrease in an unsealed reaction vessel during a reaction?

A

Some or all the reactants are solids liquids or aqueous and at least one of the products is a gas
Before reaction, any solid liquid or aqueous reactants are contained in the reaction vessel
If vessel isn’t enclosed, gas can escape from reaction vessel as its formed. It’s no longer contained in the reaction vessel so you can’t measure its mass
Total mass of stuff inside the reaction vessel decreases

101
Q

How are formulae made?

A

Combining chemical symbols of elements that combine to make compounds

102
Q

How are molecules formed?

A

If 2 or more atoms of an element chemically join

103
Q

Features of a chemical reaction (4)

A

Compounds broken up or formed
At least one new substance created
Measurable energy change
No atoms created or destroyed

104
Q

What are ions made up of?

A

Groups of atoms

Chemistry (5 decks)

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