C1.1.1 Atoms + C.1.1.2 The periodic table

C1.1.1 Atoms + C.1.1.2 The periodic table

1. All substances are made up of atoms

2. Element

   • A substance that is made up of only one type of atom
   • There are about 100 different elements
     • Which are shown in the periodic table, grouped into similar properties (a 'group' is one vertical column)
       • They are also shown as metals...
         • ...and non-metals
     • Grouped in the periodic table
       • C1.1.2 The periodic table
         • Elements in the same group have the same no. of electrons in their outer shells
           • Giving them similar properties
         • The elements in Group 0 are called the noble gases
           • They are unreactive- their atoms have a stable arrangement of electrons
     • Each element is represented by a chemical symbol e.g O for Oxygen, Na for Sodium etc..
       • (These will be given to you in the exam)

3. An atom has a small central nucleus, made up of protons and neutrons

   • Around which there are sub-atomic particles called electrons
   • Relative charges: Protons: +1. Neutron: 0. Electron: -1.
   • In an atom, no. of protons = no. of electrons
     • Meaning atoms have no overall charge
   • All atoms of a particular element have the same number of electrons
     • and atoms of different elements have different numbers of protons

4. Atomic number

   • The number of protons in an atom of an element

5. Mass number

   • The sum of the protons and neutrons in an atom

6. Electrons

   • ... each occupy particular energy levels (or 'shells')
     • They occupy the lowest available energy level (innermost available shells)
       • The first 3 innermost shells fill up as: 2, 8, 8

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