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The number of protons in the nucleus of an atom.
The total number of protons and neutrons in the nucleus.
Atoms of the same element with the same number of protons but different numbers of neutrons.
In shells (energy levels) surrounding the nucleus.
+1
0 (neutral)
-1
2
8 each
2 8 1
In order of increasing atomic number.
Groups
Periods
The same number of electrons in their outer shell giving similar chemical properties.
To the left and in the centre (transition metals).
The alkali metals
The halogens
The noble gases
They have a full outer electron shell so they do not need to gain or lose electrons.
It increases because the outer electron is further from the nucleus and more easily lost.
It decreases because the atoms are larger and attract electrons less strongly.
Ionic bonding
Covalent bonding
The electrostatic attraction between oppositely charged ions.
A shared pair of electrons between two non-metal atoms.
The electrostatic attraction between positive metal ions and a sea of delocalised electrons.
Because there are strong electrostatic forces between many oppositely charged ions requiring a lot of energy to break.
Yes because the ions are free to move and carry charge.
A giant lattice of atoms held together by many covalent bonds. Examples include diamond and silicon dioxide.
Each carbon atom forms four strong covalent bonds in a giant lattice requiring a huge amount of energy to break.
Each carbon atom forms three covalent bonds leaving one delocalised electron per atom that can carry charge.
6.02 x 10^23 particles (Avogadro's number) — the amount of substance containing this many particles.
Moles = mass (g) divided by relative formula mass (Mr)
18 (H=1x2 and O=16)
The total mass of reactants equals the total mass of products because atoms are neither created nor destroyed.
Percentage yield = (actual yield divided by theoretical yield) x 100
A measure of how much of the reactants end up as useful product. Formula: (Mr of desired product divided by sum of Mr of all products) x 100
The reactants and products of a reaction with the same number of each type of atom on both sides.
The loss of electrons.
The gain of electrons.
A list of metals in order of their reactivity from most reactive (e.g. potassium) to least reactive (e.g. gold).
When a more reactive metal displaces a less reactive metal from a compound.
Metal + acid → salt + hydrogen
Acid + alkali → salt + water
HCl
Sodium chloride (NaCl)
The breakdown of an ionic compound in solution or molten state using an electric current.
The anode (positive electrode) where negative ions lose electrons.
Hydrogen gas
Chlorine gas is produced at the anode hydrogen at the cathode and sodium hydroxide solution remains.
A reaction that releases energy (heat) to the surroundings causing the temperature to increase.
A reaction that absorbs energy from the surroundings causing the temperature to decrease.
Combustion and neutralisation.
Thermal decomposition or the reaction of citric acid with sodium hydrogencarbonate.
A diagram showing the energy of reactants and products and the activation energy of a reaction.
The minimum energy needed for a reaction to occur.
Absorbed (endothermic)
Released (exothermic)
Energy in (bonds broken) minus energy out (bonds formed). A positive result means endothermic and a negative result means exothermic.
Temperature concentration (or pressure for gases) surface area and presence of a catalyst.
Particles have more kinetic energy collide more frequently and with greater energy so more collisions exceed the activation energy.
A substance that increases the rate of reaction without being used up by providing an alternative pathway with lower activation energy.
More particles are exposed at the surface so there are more frequent collisions.
Reactions only occur when particles collide with sufficient energy (at least the activation energy) and the correct orientation.
By measuring the volume of gas produced over time or the decrease in mass over time.
CnH(2n+2)
CnH(2n)
A carbon-carbon double bond (C=C)
Add bromine water — it decolourises from orange/brown to colourless.
A mixture of hydrocarbons formed from the remains of ancient marine organisms over millions of years.
By fractional distillation — the mixture is heated and different fractions condense at different temperatures.
Breaking down large hydrocarbon molecules into smaller more useful ones using heat and a catalyst.
Carbon dioxide and water.
Carbon monoxide and/or soot (carbon particles).
A polymer formed when many small alkene monomers join together through their double bonds with no other products formed.
A single element or compound not mixed with any other substance. It melts and boils at a specific temperature.
A pure substance has a sharp precise melting point. An impure substance melts over a range of temperatures.
Separating mixtures of substances (e.g. dyes or inks) and identifying their components.
Rf = distance travelled by substance divided by distance travelled by solvent
The metal ions present in a compound based on the colour of the flame produced.
Lilac
Yellow/orange
Brick red
Green/blue-green
Add dilute nitric acid then silver nitrate solution — a white precipitate of silver chloride forms.
Add dilute acid — fizzing occurs as carbon dioxide is produced. Test the gas with limewater which turns milky.
Add dilute hydrochloric acid then barium chloride solution — a white precipitate of barium sulfate forms.
Hold a lit splint near the gas — it burns with a squeaky pop.
Hold a glowing splint in the gas — it relights.
Bubble the gas through limewater (calcium hydroxide solution) — it turns milky/cloudy.
Approximately 78% nitrogen 21% oxygen and small amounts of argon and carbon dioxide.
It was mostly carbon dioxide and water vapour with very little oxygen.
Photosynthesis by early plants and algae.
Greenhouse gases such as CO2 methane and water vapour absorb and re-emit infrared radiation from Earth's surface warming the planet.
Carbon dioxide (from burning fossil fuels) and methane (from livestock and landfill).
The total amount of carbon dioxide and equivalent greenhouse gases emitted by an individual organisation or activity.
Using renewable energy sources improving energy efficiency or reducing consumption.
A mixture contains two or more substances not chemically combined and can be separated by physical means. A compound contains elements chemically bonded together.
Add together the relative atomic masses of all the atoms in the formula.
A salt and water.
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