GCSE AQA Chemistry Atomic Structure and Bonding

GCSE AQA Chemistry Atomic Structure and Bonding

1. Atoms

   • Atoms consist of a nucleus orbited by electrons
   • Protons, neutrons and electrons are sub-atomic particles
     • Protons
       • The number of protons determines the element
         • If an element has only 1 proton it is hydrogen
         • If an element has 2 protons it is helium etc....
       • Protons have a relative charge of +
       • Protons have a relative atomic mass of 1
     • Neutrons
       • Neutrons have a relative charge of 0
       • Neutrons have a relative atomic mass of 1
     • Electrons
       • Electrons have a relative charge of -
       • Electrons have a relative atomic mass of 0
   • The nucleus is made up of protons and neutrons
   • An atom contains the same number of protons as electrons
   • The relative atomic mass is determined by the number of protons added to the number of neutrons

2. The Periodic Table

   • The periodic table is an information source that displays various properties of different elements and groups them accordingly
   • Elements are listed with symbols that represent them and are used in all formulas
     • Hydrogen's symbol is H
     • These can be one or two letters, the first always capitalised
     • Helium's symbol is He
     • These symbols are usually either taken directly from the name or from the same name in a different language
       • Gold is Au taken from its Latin name aurum
       • Hydrogen is H taken from he start of the word
   • Groups
     • Groups on the periodic table are columns
     • Groups of elements have similar properties because they have the same number of outer shell electrons
     • Group 8/0 the Noble Gases
       • Helium
       • Argon
       • Krypton
       • Radon
       • Xenon
       • Neon
       • These are unreactive because they have a full outer shell of electrons
     • Group 1 the Alkali Metals
       • Potassium
       • Francium
       • Caesium
       • Hydrogen (technically)
       • Rubidium
       • Lithium
       • Sodium
       • These are very reactive as they only have one electron in their outer shell
     • The group number is the number of electrons in the outer shell
   • Periods
     • Periods are rows on the periodic table
     • The period is the number of energy shells or layers an atom has

3. Electron shells

   • Electrons orbit the nucleus in energy layers or shells
   • The shells can only contain a certain amount of electrons
     • The first shell can contain 2 electrons
     • The second shell can only contain 8 electrons
     • The third shell can hold more than 8 electrons but at GCSE level you only need to know it can hold 8
   • Energy shells are filled from the lowest level upwards
   • Atoms want to gain a full outer shell of electrons and so this is why they react
   • Electronic Structure
     • Electronic structures are diagrams of the energy shells of an atom
     • The diagram is then described by a series of numbers that show the electron is each shell
       • Carbon is 2.4
     • Method 1
       • Draw a nucleus, no detail is necessary
         • To calculate the electronic structure find the number of protons as this is equal to the number of electrons
           • Look at the number of electrons each shell can hold and calculate how many shells you need
             • Look at the number of electrons each shell can hold and place accordingly filling from the lowest shell
     • Method 2
       • Draw the nucleus, no detail is necessary
         • Look at the period of the atom and draw that many of energy shells
           • Look at the group number and fill all the other energy shells up to the outer shell which you put the group number of electrons in

4. Ionic Bonding

   • Ions give or take electrons
   • This is held together by electromagnetic forces
   • This is between metals and non-metals
   • Giant Ionic Lattices
   • An ion is a charged particle
   • High melting point
   • High Boiling Point
   • Will carry a current in solution and melted

5. Covalent Bonding

   • This is between non-metals
   • Atoms share electrons
   • Molecules
   • Giant Structure
     • High Melting Point
     • High Boiling Point
     • No conduction of electricity (except graphite)
     • Strong covalent bonds
   • Simple Structure
     • Low Melting Points
     • Low Boiling Points
     • No conduction of electricity
     • Weak intermolecular bonds

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