C4 revision cards GCSE

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  • Created on: 12-06-13 09:56


Atoms :

- atomic structure includes a nucleus (which is made up of protons and neutrons) surrounded by electrons that go round on the orbitals.

- electrons = negative charge and mass of 0.0005, protons = positive charge and mass of 1, neutrons = no charge and mass of 1.

- atomic number = number of protons/electrons

- mass number = number of protons + number of neutrons

- isotopes are varieties of the same element --> they have the same atomic number but different mass numbers

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More on Atoms:

- atoms with an outer shell of 8 electrons have a stable electronic structure

- metal atoms form positive ions, non-metal atoms for negative ions

- ionic bonding, a metal and non-metal combine by transferring electrons to form positive ions and negative ions which then attract one another.

- the structure of sodium chloride and magnesium oxide is a giant ionic lattice in which positive ions are strongly attracted to negative ions

- sodium chloride has a high melting point and can conduct electricity when molten or in solution.

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Covalent Bonding:

- covalent bonding is between metals and non-metals, and it involves the sharing of electrons

- carbon dioxide and water are simple molecules with weak intermolecular forces between molecules

- the group number of an element is the same as the number of electrons in the outer shell

- the period in which the element belongs to corresponds to the number of occupied shells in the electronic structure

- carbon dioxide and water: have the following properties: low melting points and they do not conduct electricity

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Group 1:

- group 1 metals are also known as alkalie metals because they form alkaline solutions when reacting with metal. They also react vigorously with water to form hydrogen and hydroxide e.g.  2Na+2H2O-->2NaOH+H2

- group 1 metals have similar properties, in terms of forming positive ions (1+) with stable electronic structures.

- when group 1 metals react with water they lose an electron e.g. Li --> Li+ e-   This loss of an electron is oxidation. The reactivity of group 1 metals increased down the group.

THE FLAME TEST can be used to identify metals:

1) use of moistened flame test wire, then dip the flame test wire into a solid sample.

2) the flame test wire is then put into blue bunsen flame, and the colour of the flame is recorded

 - Lithium = red, Sodium = orange, Potassium = lilac

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Group 7:

- chlorine  = green gas, bromine = orange liquid, iodine = grey solid

- group 7 elements are known as halogens, and halogens react with group 1 metals to form halides

- halogens get LESS reactive down the group

- they can react in displacemnt reactions, the most reactive elements ends up in the compound and "kicks" the least reactive element out e.g. - chlorine displaces bromides which displaces iodides e.g. CL2 + 2KBr --> 2KCL + Br2

-  group 7 elements all have similar properties as they all have 7 electrons on their outer shell

- when halogens react, they gain an electron, this is reduction

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- compounds of a transitions element are often coloured; copper compounds are often blue, iron(II) compounds are often light green and iron(III) are often orange/brown.

- transitions elements and their compounds are often used as catalysts; iron in the Haber process, nickle in the manufacture of margarine

- transitions metal carbonates decompose to give a metal oxide and carbon dioxide - this results in colour change.

- sodium hydroxide solution is used to identify the presence of transition metal ions in solution.

- Cu2 gives a blue solid - Fe2+ gives a grey/green solid - Fe3+ gives an orange/brown solid )- all of these solids are called precipitates e.g. Cu2+  +  2OH-  -->  Cu(OH)2

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Metallic Bonding and Superconductors :

- metals have high boiling points due to strong metallic bonding.

- metallic bonding is a strong electrostatic force of attraction between positively charged metal ions and a "sea" of delocalised electrons; these delocalised electrons allow metals to conduct electricity.

- metallic bonding means to have high melting and boiling points

- superconductors are materials that can conduct electricity with little or no resistance . They form at low temperatures, and the temperature that a superconductor forms is called the critical temperature. Superconductors have no magnetic field.

- potential benefits of superconductors: - loss free power transmission   - super fast electronic circuits   - powerful electromagnets

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Water Purification:

- 3 stages to water purification: 1) sedmentation  2) filtration using sand  3) chlorination

- lead pipes lead to lead being in the water; nitrates enter the water system from fertiliser run off; pesticides enter the water system from pesticides spraying near water courses.

- sea water is not used as drinking water as it would be too expensive to purify it

- to test for the presence of sulphate ions, add barium chloride - a positive result will show a white precipitate// barium chloride + magnesium sulphate --> barium sulphate (white ppt) + magnesium chloride --- BaCl2 (aq) + MgSO4 (aq) --> BaSO4 (a) + MgCl2 (aq)

- to test for the presence of halidides, add silver nitrate: chloride = white precipitate, bromide = cream precipitate, iodide = yellow precipitate // silver nitrate + sodium chloride --> silver chloride (white ppt) + sodium nitrate --- NaCl (aq) + AgNO3 (aq) --> AgCl (a) + NaNO3 (aq)

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