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Edexcel Additional Chemistry (C2) Revision – Mrs. Moon
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Mendeleev Explain how Mendeleev arranged the elements in a periodic table Predict the properties of missing elements Classify elements as metals or non-metals
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The structure of an atom
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The structure of an atom (again!) Learn this! particlepositionchargemasssymbol protonnucleus+11p Neutronnucleus01n electronShell/orbital~0e
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The Periodic table – you don’t need to remember them, just know what the numbers mean
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What do the numbers mean? Atomic Number (number of protons) Element symbol Atomic mass The Atomic mass is always the biggest number Atomic mass = number of protons + number of neutrons
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Columns down = groups And indicate how many electrons are in the outer shell Rows across are called = periods and indicate how many Electron shells the element has
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Isotopes - H
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H paper - Isotopes An isotope has the same number of protons, but a different number of neutrons – so – The atomic number will be the same, but the mass number is different
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Electron (always negative) Atoms have the same number of electrons as they do protons/Atomic number Helium – Atomic number 2, proton number 2, electron number 2 Neon – atomic number 10, proton number 10, electron number 10 Simples!
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Electron shells Electrons are like soldiers on parade– they are arranged in a very specific order! 2, 8, 8
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Period table and electron shells
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Ions are atoms that have lost or gained electrons Atoms like full outer shells and chemical reactions are atoms achieving this One way is by becoming an ion
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Ionic bonds Ionic Bonds when electrons have been given away or received, those atoms become either positive or negative Positives and negatives attract Forming an ionic bond
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Ionic compounds Ionic compounds can keep growing and growing and become very big – like salt Ionic compounds are formed between metals and non-metals
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Ionic bonds Cations Anions What are cations? Cations are atoms which loses electrons to obtain a noble gas structure. Hence, it has a positive charge. e.g A magnesium atom (An atom of a metal) loses two electrons to form a magnesium ion in its compound. What are anions? Anions are atoms which gains electrons to obtain a noble gas structure. Hence, it has a negative charge. e.g A chlorine atom (An atom of a non-metal) gains an electron to form a chloride ion in its compound.
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Ionic compounds Working out a formula
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Formula of ionic compounds Ca looses 2 electrons So becomes +2 Cl gains 1 electron so becomes -1 (remember electrons are -1=negative To make a zero charge you will need 2 x Cl-1 to cancel out Ca+2 Try the last 3 yourself
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Properties of ionic compounds H paper To conduct electricity an ionic compound must: Contain charged particles (be positive or negative) Be free to move (in solution)
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Ion tests
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Some key words to know Soluble – will dissolve into a liquid Insoluble – will not dissolve in a liquid A salt – and acid + an alkali Precipitates – an insoluble solid appears at the end of a reaction State symbols; (s) = solid; (l) = liquid; (g) = gas; (aq) = aqueous/in water
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Covalent bonds – share electrons to gain a full outer shell
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Properties of covalent substances
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Covalent bonds
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Properties of covalent structures H paper Most covalent compounds are tiny molecules and gases e.g. carbon dioxide Diamond and graphite are unusual as they are covalent, but giant compounds A why is graphite used as a lubricant (reduces friction – makes things slippy)
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Properties of covalent substances
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Miscible or immiscible
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Metallic bonding
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Alkali Metals
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Halogens
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Nobel Gases Structure Noble gases are in group 0. This means they have a full outer electron field, this makes them un-reactive. This also means they are monatomic - do not join with other elements that are the same, but are single and alone. As you move down the periods, the gases have an increasing boiling point and also density. Uses Probably the most famous noble gas is Helium, as it is used in balloons. This is because it 'floats' due to the fact it is less dense than air, so rises above it, and is completely safe since it is un-reactive. However, the densities increase as you go down the group.
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Rates of reaction
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Collision theory
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