Atoms, Elements and Compounds

Only available on StudyMode
  • Download(s) : 42
  • Published : March 5, 2013
Open Document
Text Preview
AQA GCSE Chemistry Unit 1

C 1: Fundamental ideas:
C 1.1. Atoms, elements and compounds:
* All substances are made up of atoms.
* Elements contain only one atom.
* Compounds contain more than one atom.
* An atom has a tiny nucleus in its centre, surrounded by electrons. C 1.2. Atomic structure:
* Atoms are made up of protons, neutrons and electrons.
* Protons and electrons have equal and opposite electrical charges. Protons are positively charged, and electrons are negatively charged. * Neutrons have no electrical charge. They are neutral.

* Atomic number = number of protons (number of electrons.) * Mass number = number of protons and neutrons.
* Atoms are arranged in the periodic table in order of their atomic number. C 1.3. The arrangement of electrons in atoms:
* The electrons in an atom are arranges in energy levels or shells. * Atoms with the same number of electrons in their outermost shell belong in the same group of the periodic table. * The arrangement of electrons in the outermost shell of an elements atom determines the way that element reacts. * The atoms of the unreactive noble gases (in group 0) all have very stable arrangements of electrons. C 1.4. Forming bonds:

* When atoms from different elements react together they make compounds. The formula of a compound shows the number and type of atoms that have bonded together to make that compound. * When metals react with non-metals, charged particles called ions are formed. * Metal atoms form positively charged atoms. Non-metals form negatively charged atoms. These oppositely charged ions attract each other in ionic bonding. * Atoms of non-metals bond to each other by sharing electrons. This is called covalent bonding. C 1.5. Chemical equations:

* As no new atoms are ever created or destroyed in a chemical reaction: total mass of reactants = total mass of products. * There is the same number of each type of atom in each side of a balanced symbol equation. C 2: Rocks and building materials:

C 2.1. Limestone and its uses:
* Limestone is made mainly of calcium carbonate.
* Limestone is widely used in the building industry.
* The calcium carbonate in limestone breaks down when we heat it strongly to make calcium oxide and carbon dioxide. The reaction is called thermal decomposition. C 2.2. Reaction of carbonates:
* Carbonates react with dilute acid to form a salt, water and carbon dioxide. * Limewater turns cloudy in the test for carbon dioxide gas. A precipitate of insoluble calcium carbonate causes the cloudiness. * Metal carbonates decompose on heating to form the metals oxide and carbon dioxide. C 2.3. The ‘limestone reaction cycle’:

* When water is added to calcium oxide it produces calcium hydroxide. * Calcium hydroxide is alkaline so it can be used to neutralize acids. * The reactions of limestone that you need to know are shown in the limestone cycle. C 2.4. Cement and concrete:

* Cement is made by heating limestone with clay in a kiln. * Mortar is made by mixing cement and sand and water.
* Concrete is made by mixing crushed rocks or small stones called aggregate, cement and sand with water. C 2.5. Limestone issues:
* There are good and bad points about quarrying for limestone. For example, more jobs will be created, but it will leave a large scar on the landscape. * Limestone cement and concrete all have useful properties for use as building materials, but the mining and processing of limestone and its products has a major effect on our environment. C 3: Metals and their uses:

C 3.1. Extracting metals:
* A metal ore contains enough of the metal to make it economic to extract the metal. Ores are mined and might need to be concentrated before the metal is extracted and purified. * We can find gold and other unreactive metals in their native state. * The reactivity series helps us to decide the best way to extract a metal...
tracking img