C1 Atomic Structure

C1.1 Atoms

• All substances are made up of atoms
• The periodic table list all the chemical elements
• eight main groups each containing elements with similar chemical properties
• Elements contain only one type of atom
• Compounds contain more than one type of atom
• An atom has a tiny nucleus at its centre, surrounded by electrons
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• Bildunterschrift: Compound

C1.2 Chemical Equations

• No new atoms are ever created or destroyed in a chemical reactions
• total mass of reactants = total mass of products
• There is the same number of each type of atom on each side of a balanced symbol equation
• You can include state symbols to give extra information in balanced symbol equations
• s - solid
• l - liquid
• g - gas
• aq - aqueous
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• Bildunterschrift: Equation for respiration

C1.3 Separating mixtures

• A mixture is made up of two or more substances that are not chemically combined together
• Mixtures can be separated physically
• Filtration
• Crystallisation
• Simple distillation
• Separation
• Fractional distillation
• Chromatography
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• Bildunterschrift: Simple distillation

C1.4 Fractional Distillation and Paper Chromatography

• Fractional distillation is an effective way of separation miscible liquids using a fractioning column
• It is possible because of the different boiling points in a mixture
• Paper chromatography separates pictures of substances dissolved in a solvent as they move up a piece of chromatography paper
• They are separated because of their different solubilities in the solvent used
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• Bildunterschrift: Fractional distillation

C1.5 History of the Atom

• Ideas about atoms have changes over time
• New evidence has been gathered from the experiments of scientists who have used their modes of the atom to explain their observations and calculations
• Key ideas were proposed successively by Dalton, Thomson, Rutherford and Bohr before getting the model of the atom we use in GCSE
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• Bildunterschrift: Atoms throughout time

C1.6 Structure of the Atom

• Atom are made of protons (+1), neutrons (0) and electrons (-1)
• Relative mass of a proton and a neutron are both 1
• Atoms contain an equal number of protons and electrons and so carry no overall charge
• Atomic number = number of protons (= number of electrons)
• Mass number = number of protons + number of neutrons
• Atoms of the same element have the same number of protons in their atoms
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• Bildunterschrift: Structure of an atom

C1.7 Ions, atoms and isotopes

• Atoms that gain electrons form negative ions (anions)
• Atoms that lose electrons form positive ions (cations)
• The atomic number is the small number in the periodic table and the mass number is the larger one
• Isotopes are atoms of the same element with different numbers of neutrons
• Identical chemical properties
• Physical properties, such as density, could be different
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• Bildunterschrift: Magnesium

C1.8 Electronic Structure

• The electrons in an atom are arranges in energy levels or shells
• The lowest energy shell, the 1st shell, can hold up to 2 electrons
• The next energy shell, the 2nd shell, can hold up to 8 electrons
• The number of electrons in the outermost shell of an element determines the way in which that element reacts
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• Bildunterschrift: Electronic structure of magnesium