Chemistry Flashcards
(229 cards)
1
Q
Name the 3 sub-atomic structures in an atom.
A
- Proton
- Neutron
- Electron
2
Q
What is a compound?
A
When 2 or more elements combine together.
3
Q
Name the 4 state symbols in a symbol equation.
A
- (s) Solid
- (l) Liquid
- (aq) Aqueous
- (g) Gas
4
Q
What is the law of the conservation of mass?
A
A law which states that no atoms are lost or made during a chemical reaction. So mass of reactants = mass of products.
5
Q
Name the 4 main methods of seperating mixtures.
A
- Filtration
- Crystallisation
- (Fractional) Distillation
- Chromatography
6
Q
What is commonly seperated using chromatography?
A
Food dyes.
7
Q
Who suggested the idea of atoms?
A
John Dalton (1803)
8
Q
Who discovered the electron?
A
JJ Thomson (1897)
9
Q
Who proposed the ‘plum pudding’ model?
A
JJ Thomson (1904)
10
Q
Who (2 people) fired a beam of alpha particles at a thin gold leaf to test the plum pudding model?
A
Hans Geiger and Ernest Marsden (1905)
11
Q
Who made the nuclear model?
A
Ernest Rutherford (1911)
12
Q
Who discovered the neutron?
A
James Chadwick (1932)
13
Q
What is the overall charge of a proton, a neutron and an electron?
A
- Proton: +1
- Neutron: 0
- Electron: -1
14
Q
What is the atomic number?
A
The number of protons in an atom. (And therefore the number of electrons too.)
15
Q
What is the mass number?
A
The total number of protons and neutrons in an atom.
16
Q
What is an ion?
A
A charged atom (or group of atoms) when it transfers or shares electrons.
17
Q
What is an isotope?
A
An atom of the same element but different number of neutrons.
18
Q
How are electrons generally arranged in an atom?
A
In shells, the first shell can hold up to 2 electrons. Any shell after the first can carry up to 8 electrons.
19
Q
What is another phrase for group 0 elements?
A
Noble gases.
20
Q
What are the 3 states of matter?
A
- Solid
- Liquid
- Gas
21
Q
How are particles represented in diagrams?
A
Small, solid spheres.
22
Q
What are the limitations of the particle model?
A
- Particles can be atoms, ions or molecules.
- Particles vary in size.
- Particles can contain many atoms.
- Particles are not solid or spherical.
23
Q
What is covalent bonding?
A
When 2 atoms of non-metallic elements join together by sharing electrons.
24
Q
What is ionic bonding?
A
When a atoms of metallic and non-metallic elements join together by transferring electrons.
25
What are dot and cross diagrams?
Diagrams with dots representing electrons from 1 ion, and crosses representing electrons from the other.
26
What is a giant structure? (Or giant lattice.)
When the oppositely charged ions of metallic and non-metallic elements get attracted together to form a giant molecule.
27
Why do ionic solids have high melting points?
They have many strong electrostatic forces from the oppositely charged ions.
28
Why can ionic substances conduct electricity when molten or dissolved in water?
Ions can move freely and carry a charge.
29
What are intermolecular forces?
Forces which occur between molecules. These forces get stronger as molecules get larger.
| (Not to be mistaken by the bonds between ions.)
30
Why do smaller molecules have lower melting and boiling points?
They have weaker intermolecular bonds which require less energy to break.
31
What is a polymer?
Large molecules made up of repeating units. They have relatively strong intermolecular forces.
32
How are giant covalent structures held together?
Through strong covalent bonds.
33
Why does diamond have a very high melting point?
Each carbon atom forms strong covalent bonds with 4 other carbon atoms which require lots of energy to break.
34
What are delocalised electrons?
Electrons which move freely throughout a structure, found in covalent and metallic bonds.
35
Why is graphite soft and slippery?
It is formed in layers, which have weak intermolecular forces between them.
36
What are fullerenes?
Structures where carbon atoms join together to make large hollow shapes.
37
What was the first fullerene discovered?
Buckminsterfullerene (C₆₀)
38
What can fullerenes be used for?
- Drug delivery
- For lubrication
- As a catalyst
39
What is graphene?
1 single layer of graphite which is 1 carbon atom thick. Excellent conductor of electricty, low density and very strong for its mass.
40
How are atoms arranged in a metal?
Closely packed in regular patterns.
41
How are metallic molecules held together?
Delocalised electrons which attract the positively charged metals.
42
What are alloys?
Mixtures of metals or metals with other elements.
43
Why are alloys harder than pure metals?
The different sized atoms distort the regular patterns, making it more difficult for the layers to slide over each other.
44
Why do metals have high melting and boiling points?
They have electrostatic forces between the positive metal ions and delocalised electrons in all directions. These forces require a lot of energy to break.
45
What is a nanoparticle?
Particles which range between 1-100 nanometres (nm)
46
What is the conversion between nanometres and metres?
1nm = 1x10^-9m
(Or 1 billionth of a metre.)
47
What are coarse particles also known as?
Dust
48
Why are nanoparticles very reactive?
Large surface area
49
What can nanoparticles be used for?
- Deodorants and face creams where they are absorbed deep into skin.
- Medicine, carbon nanocages can deliver drugs in the body. Coatings of silver nanoparticles can also help protect against bacteria on wounds.
- Computers, nanowires provide improved memory capacities and speeds.
- Catalysts, their large surface area makes them effective catalysts.
50
What are the risks of nanoparticles?
- Breathing in tiny particles can damage lungs and enter the bloodstream.
- Accumulation of nanoparticles in aquatic life.
51
How do you calculate the relative formula mass of a substance?
Add up the mass number of all atoms in the molecule.
52
What is the Avogadro constant and what does it mean?
**6.02 × 10²³**
It is the number of atoms, molecules or ions in 1 mole of any substance.
53
What is the equation for moles?
moles = grams / Ar
**OR**
moles = grams / Mr
54
What is the formula for mass (in grams) in chemical calculations?
grams = moles x Mr
**OR**
grams = moles x Ar
55
What is the limiting reactant?
The reactant which is used up first in a reaction.
56
What is a percentage yield?
The percentage of product produced compared to maximum of what could have been produced.
57
What is the equation for percentage yield?
% yield = (mass of product / maximum mass possible) x 100.
58
What is atom economy?
The percentage of atoms which react that end up in the product.
59
What is the equation for atom economy?
Atom economy = (Mr of desired product / sum of Mr of reactants) x 100
60
What is the formula for concentration?
Concentration = mass / volume
61
What are the 2 main units of concentration and their conversion rate?
g/dm³ or g/cm³
1g/cm³ = 1000g/dm³
62
What is the volume occupied by 1 mole of gas?
24dm³ (24,000cm³)
At room temperature.
63
What is the equation for moles of gas?
moles = volume (dm³) / 24dm³
64
What is oxidation and reduction?
| (In terms of electrons.)
Oxidation is loss of electrons.
Reduction is gain of electrons.
| (Remember OILRIG)
65
What is the reactivity series?
A list of the order of reactivity of metals, with most reactive at the top and least reactive at the bottom.
66
What is a displacement reaction?
When a more reactive metal replaces a less reactive metal.
67
What is produced when a metal reacts with an acid?
A salt is formed.
68
What type of reaction occurs between a base and a salt?
Neutralisation reaction.
69
What is a base?
A substance that reacts with an acid to neutralise it and produce a salt.
70
What is an alkali?
A substance that produces hydroxide ions when dissolved in water.
71
What compound is produced in every neutralisation reaction?
Water
72
What pH value is classified as 'neutral'?
7
73
What colours are acidic solutions on the pH scale?
Red, orange, yellow
74
What colour is a neutral solution on the pH scale?
Green
75
What colour are alkaline solutions on the pH scale?
Blue, purple
76
What is used to measure pH?
Universal indicator.
77
What is the difference between strong and weak acids?
Strong acids completely ionise in aqueous solutions. Weak acids partially ionise in aqueous solutions.
78
What is the relationship between pH value and concentration of hydrogen ions?
As pH increases by 1, concentration of hydrogen ions decrease by a factor of 10. (i.e. divide by 10.)
79
What is electrolysis?
A process that uses electricity to break down ionic compounds into elements.
80
What is the name for a substance that has been broken down with electrolysis?
An electrolyte
81
What is the:
1) Anode
2) Cathode
1) Positive electrode
2) Negative electrode
82
What charged ions go to:
1) Anode
2) Cathode
and why?
1) Negatively charged ions
2) Positively charged ions
Opposite charges attract.
83
What do molten ionic compounds produce at the anode and at the cathode?
Anode: non-metal element
Cathode: metal element
84
What is the order of discharge at the anode?
Halide ions > hydroxide ions > other negatively charged ions
85
What is the order of discharge at the cathode?
In the reverse order of the reactivity series.
86
What unique products can aqueous solutions produce unlike molten compounds in electrolysis?
Hydroxide ions and hydrogen ions
87
Where does aluminium come from?
Bauxite ore
| (Mostly aluminium oxide)
88
What is the melting point of aluminium and how is it reduced to save energy?
Over 2000°C.
Cryolite can be mixed with aluminium oxide to reduce melting point to around 850°C.
89
Why does the anode need to be replaced regularly when electrolysing aluminuim?
Oxygen is attracted to the anode, and this burns the carbon anodes, burning them away.
90
How can rate of reaction be read from a graph?
The gradient
91
What is the equation for rate of reaction?
Rate of reaction =
Quantity of reactant used or quantity of product formed / Time taken
92
What is the collision theory?
Particles can only react if they collide.
93
What is the phrase for minimum energy required to start a reaction?
Activation energy
94
How can the rate of reaction be increased?
- Higher temperature
- Higher concentration of reactants
- Increasing pressure of gases
- Increasing surface area
- Using a catalyst
95
Why does increasing the temperature increase rate of reaction?
Particles collide more often and with more energy.
96
What do catalysts do?
Increase rate of reaction by providing a different reaction pathway with lower activation energy.
97
What is a hydrocarbon?
A molecule containing carbon and hydrogen **only**.
98
What is the difference between an alkene and an alkane?
An **alkene** has twice as many hydrogen atoms than carbon atoms.
An **alkane** has twice as many plus two hydrogen atoms than carbon atoms.
99
What is a saturated hydrocarbon?
A hydrocarbon which contains only carbon-carbon single bonds, no double bonds.
100
How is fractional distillation used for crude oil?
The different sizes of hydrocarbons have different boiling points, so they will get seperated by condensing at their given temperature.
101
What are the properties of smaller hydrocarbons compared to larger hydrocarbons?
- Lower boiling points
- More volatile (evaporate easier)
- More flammable (ignite easier)
- Less viscous (flow easier / runny)
102
What is a pure substance?
A substance which is made of one type of element / compound.
103
What is a formulation?
A mixture which is designed to do something useful.
104
What and where are the 2 phases in chromatography?
Mobile phase: solvent
Stationary phase: paper
105
What is the formula for retention factor in chromatography?
Distance moved by substance /
Distance moved by solvent
106
What is the test for hydrogen?
Lit splint into test tube. Hydrogen rapidly burns with a squeaky pop if present.
107
What is the test for oxygen?
Glowing splint into test tube. Splint relights if oxygen is present.
108
What is the test for carbon dioxide?
Bubble gas through limewater. Limewater turns milky if carbon dioxide is present.
109
What is the word formula for limewater?
Calcium hydroxide
110
What is the test for chlorine?
Damp blue litmus paper held at mouth of a test tube. Damp blue litmus paper will bleach and turn white if chlorine is present.
111
What colour flame will the following ions produce when put into a Bunsen flame?
- Lithium
- Sodium
- Potassium
- Calcium
- Copper
Lithium: Crimson
Sodium: Yellow
Potassium: Lilac
Calcium: Orange-red
Copper: Green
112
What colour precipitates form when the following metal ions are added to sodium hydroxide?
- Copper (II)
- Iron (II)
- Iron (III)
Copper (II): Blue precipitate
Iron (II): Green precipitate
Iron (III): Brown precipitate
113
What forms when sodium hydroxide is added to aluminium, calcium or magnesium ions?
And how can aluminium be distinguished from calcium and magnesium?
A white precipitate forms.
Adding excess sodium hydroxide to aluminium ions will result in the white precipitate dissolving and forming a colourless solution.
114
What is the test for carbonate ions?
Add dilute hydrochloric acid to the substance and see if it fizzes. If so, and the gas turns limewater cloudy, then carbonate ions are present.
115
What forms when the following ions are mixed with dilute nitric acid and then silver nitrate solution?
- Chloride ions
- Bromide ions
- Iodide ions
Chloride: white precipitate
Bromide: cream precipitate
Iodide: yellow precipitate
116
What is the test for sulfate ions?
Add dilute hydrochloric acid and then barium chloride. If a white precipiate forms, then sulfate ions are present.
117
What is flame emission spectroscopy and what does it do?
It is an instrumental method that chemists use to analyse samples for metal ions.
The sample is heated through a flame. The light produced is analysed by passing it through a spectroscope. Each type of metal has its own pattern, called its line spectrum. You can compare the line spectra with a database to analyse the metal ions present.
118
When do scientists believe the Earth was formed?
4.6 billion years ago
119
How do scientists think gases formed in the early atmosphere?
Intense volcanic activity
120
What did Earth's early atmosphere consist of?
- Mainly carbon dioxide
- Some water vapour
- Some nitrogen gas
- Traces of methane
- Traces of ammonia
121
How were oceans formed?
Water vapour in the early atmosphere condensed as the Earth cooled down.
122
What percentages of each gas make up our atmosphere today?
- Nitrogen (78%)
- Oxygen (21%)
- Argon (1%)
- Carbon dioxide (0.04%)
123
How was carbon dioxide removed in the early atmosphere?
- Dissolved in the oceans
- Photosynthesis by algae and plants
124
What are the greenhouse gases in today's atmosphere?
- Carbon dioxide
- Water vapour
- Methane
125
How do greenhouse gases heat up the Earth?
The gases absorb infrared radiation. So energy radiated from the surface of Earth are trapped in the atmosphere and the temperature rises.
126
How is methane in the air increasing?
- More animal farming leading to more emissions and decomposing waste.
- Increased waste, so more decomposition of rubbish in landfill sites.
127
What are the consequences of rising levels of greenhouse gases?
- Rising sea levels due to melting ice caps
- More frequent and severe storms
- Changes in temperature
- Changes in distribution of rainfall
- Impact on food-producing capacity
- Changes to distribution of wildlife species
128
What is the carbon footprint of a product?
The total amount of greenhouse gases emitted by a product over its full life cycle.
129
How can carbon footprint be reduced?
- Alternative energy
- Conserving energy
- Carbon neutral fuels
- Taxing carbon usage
- Planting trees
- Carbon capture and storage
- Plant-based diets
130
What are the problems in reducing carbon footprints?
- Disagreements on causes and consequences of climate change
- Incomplete international co-operation
- Cost implications in all industries
- Hindering growth of industries in poorer countries
- Lack of public information
131
What forms when pure hydrocarbons are burnt?
- Carbon dioxide
- Water
132
What is incomplete combustion?
When there is insufficient oxygen present during combustion, and hydrocarbons burn to form unburnt hydrocarbons and carbon monoxide instead of carbon dioxide.
133
How is carbon monoxide dangerous?
It is toxic. It is also colourless and odourless. When inhaled, it binds with haemoglobin in the blood and is carried around instead of oxygen.
134
What can cause acid rain?
- Sulphur dioxide
- Nitrogen oxide
135
What are finite resources?
Resources that are being used up quicker than they can be replaced.
136
What are renewable resources?
Resources that can be replaced at the same rate that they are being used up.
137
What is fresh water?
Water that contains dissolved minerals (salts).
138
What is potable water?
Water which is safe to drink by humans.
139
How can water be treated to make it potable?
- Passing it through filter beds to remove solid particles.
- Sterilisation by adding chlorine, ozone or passing ultraviolet light through the water.
140
What is desalination?
The removal of salt from seawater.
141
How can seawater / salty water be made potable.
Desalination
142
How can pure water be made?
Distillation
143
What is sewage?
The general name for waste water from homes, businesses etc.
144
What is the steps for treating sewage?
1) Screening: removing large solid objects and grit.
2) Sedimentation: allows tiny particles to be settled out from still water, producing sewage sludge and effluent.
3) Sewage sludge is digested anaerobically by specific bacteria.
4) The effluent is treated with aerobic bacteria to reduce the volume of solid waste.
145
What can dried sludge be used for?
Renewable energy or as a fertiliser.
146
What does sludge contain?
- Water
- Organic matter
- Human waste
- Suspended solids
- Dissolved compounds
147
How can copper be produced from copper-rich ores?
- Smelting and purifying
- Bioleaching
- Phytomining
148
What is phytomining?
Growing plants on soil containing
low-grade copper ore. The plant absorbs the copper ions. Then, the plant is burnt and copper is extracted from the ash.
149
What is bioleaching?
Using bacteria to produce solutions of copper compounds (leachate) from waste copper ore.
150
How can copper be extracted from copper compounds?
- Displacement using scrap iron
- Electrolysis
151
What are Life Cycle Assessments? (LCA)
A method to evaluate the environmental impact of a product or process over its entire life cycle.
152
What are the 4 stages in LCA?
1) Raw material extraction
2) Manufacturing
3) Use / reuse / maintenance
4) Recycle / waste management
153
What are the aims of the 'reduce, reuse and recycle' campaign?
- Reduce the use of limited resources
- Reduce the use of limited energy sources
- Produce less waste
- Reduce pollution
154
How is recycling metal beneficial?
The limited reserves of metal ores and be conserved.
155
What is an exothermic reaction?
A reaction where energy is released from the chemicals into the surroundings.
156
What is an endothermic reaction?
A reaction where energy is taken in from the surroundings into the chemicals.
157
What can exothermic and endothermic reactions be used for?
Exothermic reactions to heat things up.
Endothermic reactions to cool things down.
158
What is a reaction profile diagram?
A diagram which shows us the relative amounts of energy contained in the reactants and the products.
159
How would an exothermic reaction look in a reaction profile diagram?
A small peak for to reach activation energy, and then a large decrease in energy. The reactants have more energy than the products.
160
How would an endothermic reaction look in a reaction profile diagram?
A rapid increase in energy until a high peak to reach activation energy, and then a small decrease. The reactants have less energy than the products.
161
What is activation energy?
The minimum amount of energy required to start a chemical reaction.
162
What type of reaction is breaking a bond and why?
**Endothermic**
Energy is taken in from the surroundings.
163
What is the term for amount of energy required to break a bond?
Bond energy
164
What are bond energies measured in?
**kJ / mol**
(Kilojule per mole)
165
How can 2 metals be used to make a battery?
2 different metals connected together with a wire are dipped into a salt solution. Electrons will flow through the wire from the more reactive metal to the less reactive metal. The flow of electrons is an electrical current. A greater difference in reactivity produces a higher voltage.
166
Why do batteries with 2 metals eventually stop producing a current?
One of the reactants are completely used up.
167
How do rechargable cells work?
The cell is connected to a power supply which reverses the reactions that occur at each electrode, which regenerates the original reactants.
168
What is a fuel cell?
A device which generates elecrticity by reacting hydrogen and oxygen to convert fuel and oxygen to electricity, heat and water.
169
What are the advantages and disadvantages of hydrogen fuel cells?
**Advantages**
- Do not need to be electrically recharged.
- No pollutants produced.
- Can be a range of sizes for different uses.
**Disadvantages**
- Hydrogen is highly flammable.
- Hydrogen is sometimes produced for the cell from non-renewable sources.
- Hydrogen is difficult to store.
170
What is rusting?
The corrosion of iron when it reacts with water and oxygen.
171
What is galvanised iron and why is it used?
It is iron which is covered by a layer of zinc. Zinc is more reactive than iron so any water and oxygen will react with the zinc rather than the iron. This is called **sacrificial protection**.
172
What are the 2 methods of cracking hydrocarbons?
- Steam cracking
- Catalytic cracking
173
What is steam cracking?
Heating a mixture of hydrocarbon vapour with steam at very high temperatures.
174
What is catalytic cracking?
Heating a mixture of hydrocarbon vapour and passing it over a hot catalyst (aluminium oxide).
175
What is titration used for?
Finding the exact volume of acid and alkali that react with each other
176
What is a reversible reaction?
Reactants which create products which can react again to create the reactants again
177
What is equilibrium?
| (In a reversible reaction)
When the rate of the forward reaction is equal to the rate of the reverse reaction.
Both continue to happen, but the amount of reactants and products remain constant
178
What is Le Chatelier's Principle?
When the conditions are changed in a system at equilibrium, the position of the equilibrium shifts to cancel out the change.
179
What happens to a reversible reaction when the pressure:
1) Increases
2) Decreases
**Increase:** the reaction producing less molecules is favoured.
**Decrease:** the reaction producing more molecules is favoured.
180
What happens to a reversible reaction when the temperature:
1) Increases
2) Decreases
**Increase:** Endothermic reaction is favoured
**Decrease:** Exothermic reaction is favoured
181
What is the Haber Process?
A chemical process that creates ammonia by reacting hydrogen and nitrogen.
182
What are the ideal conditions for the Haber Process?
- 450°C temperature
- 200 atmospheres of pressure
- Iron catalyst
183
What is ammonia mainly used for?
Fertilisers
184
What is the formula for hydroxide?
OH¯
185
What is the formula for nitrate?
NO₃¯
186
What is the formula for carbonate?
CO₃²⁻
187
What is the formula for sulphate?
SO₄²⁻
188
What is the formula for phosphate?
PO₄³⁻
189
What is the formula for ammonium?
NH₄⁺
190
What is the formula for ammonia?
NH₃
191
Why does the Haber Process use 200 atmospheres as its pressure?
It allows a reasonably quick rate of reaction, while keeping costs down
192
Why does the Haber Process use 450°C as its temperature?
The forward reaction is exothermic, so a high temperature would decrease the yield of ammonia. However, a higher temperature allows a quicker rate of reaction.
193
Why does the Haber Process use an iron catalyst?
It increases the rate of both the forward and reverse reactions, so the yield of ammonia isn't affected, but ammonia production is sped up.
194
What is an NPK fertiliser and why are they needed?
An NPK fertiliser is a fertiliser containing formulations of compounds to provide nitrogen, phosphorus and potassium in appropriate proportions.
They are needed to provide plants with nitrogen (N), phosphorus (P) and potassium (K), which are needed for healthy growth.
195
What is the source of nitrogen in NPK fertilisers?
Ammonia, from the Haber process. Ammonia is reacted with acids to make fertilisers such as ammonium nitrate.
196
What is the source of phosphorus in NPK fertilisers?
Deposits of phosphate containing rock, which are mined from the ground. The rock isn't soluble in water, so it is treated with nitric acid to produce phosphoric acid. The acid is then neutralised with ammonia to create ammonia phosphate.
197
What is the source of potassium in NPK fertilisers?
Potassium salts, such as potassium chloride, are mined. They are soluble in water, so can be seperated from inpurities and used directly.
198
What is a functional group?
A specific group of atoms that are present within organic molecules and are responsible for the characteristic properties and reactivity of the molecules.
*Examples of functional groups include alcohols and carboxylic acids*
199
What is a homologous series?
A 'family' of organic compounds with the same functional group
200
What is the test for alkenes?
An alkene will turn orange-brown bromine water colourless as the bromine reacts with the
carbon-carbon double bond.
201
What is the displayed formula for alkanes?
**C**n **H**2n+2
202
What is the displayed formula for alkenes?
**C**n **H**2n
203
What is the displayed formula for alcohols?
**C**n **H**2n+1 **OH**
204
What is the displayed formula for carboxylic acids?
**C**n **H**2n+1 **OOH**
205
What is the functional group for alkanes?
C-C single bond
206
What is the functional group for alkenes?
C=C double bond
207
What is the functional group for alcohols?
-OH bonds
208
What is the functional group for carboxylic acids?
-COOH bonds
209
What is the functional group for an ester?
-COO-
210
How are esters formed?
A condensation reaction between an alcohol and a carboxylic acid
211
What do alcohols produce when burnt in air?
- Carbon dioxide
- Water
212
What are the main uses of esters and why?
The main uses of esters are for flavourings and perfumes. This is because of their pleasant fruity smells.
213
What is a monomer?
Small molecules which are used to make polymers
214
What is a repeating unit?
The smallest part of a polymer which is repeated
215
What is a thermosoftening polymer?
A polynmer that softens when heated. They are made of indiviudal polymer chains that are tangled together
216
What is a thermosetting polymer?
A polymer that doesn't melt when heated. They have strong covalent bonds forming 'cross-links' between their polymer chains
217
What is addition polymerisation?
Formation of polymers using thousands of alkene molecules which join together. Forms no by-products.
218
What is condensation polymerisation?
Formation of polymers due to condensation of more than one different monomers. (A diol and a dicarboxylic acid.) Forms by-products.
219
What are concordant results?
Results within 0.1cm³ of each other
220
What did John Newland do?
In 1864, he noticed every eighth atom was similar when ordered in atomic weight, so he produced a table showing his **law of octaves**. But not all elements had been discovered yet.
221
What did Dmitri Mendeleev do?
In 1869, he arranged all 50 elements which were discovered at the time in a table. He left gaps for elements which weren't discovered yet. He also noticed patterns in properties which allowed him to predict properties of undiscovered elements.
222
What are Group 1 elements called?
Alkali metals
223
What are the properties of Group 1 elements?
- Soft solids at room temp
- Relatively low melting and boiling points which decrease as you go down the group
- Reactivity increases as you go down the group
- Low densities
- 1 electron in outer shell
- Form 1+ ions
224
What are Group 7 elements called?
Halogens
225
What are the properties of Group 7 elements?
- Relatively low melting and boiling points which increase as you go down the group
- Poor conductors of thermal energy and electricity
- Bond covalently with non-metals
- 7 outer shell electrons
- Form 1- ions
226
Why does reactivity increase as you go down Group 1?
Outer shell electrons are further away from the nucleus as you go down the group, so will endure a weaker attraction force. Attraction from the nucleus is also reduced by shielding of the inner shells. So, as you go down the group electrons will be able to escape the atom more easily.
227
Why does reactivity decrease as you go down Group 7?
Outer shell electrons are further away from the nucleus as you go down the group, so will endure a weaker attraction force. Attraction from the nucleus is also reduced by shielding of the inner shells. So as you go down the group, incoming electrons will have a weaker attraction force to the atom.
228
What are the properties of transition metals?
- Good conductors of thermal energy and electricity
- Hard and strong
- High densities
- High melting points (except mercury)
- Less reactive than Group 1 metals
- Can form ions with different charges
- Compounds are often brightly coloured
- Important for industrial use as catalysts
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What does a catalytic converter do?
Reduces harmful emissions from a car’s exhaust by converting toxic gases into less harmful substances. They use *platinum*, *pallidium* or *rhodium* as catalysts.
