Atoms & The Periodic Table

Atoms & The Periodic Table

1. Atoms

   • Electrons
     • Negative Charge
     • Move around the Nucleus
     • Occupy Shells
     • If Electrons are added/removed the atom then becomes an Ion
   • Nucleus
     • In the middle of an Atom
     • Contains Protons & Neutrons
       • Positive Protons
         • Number of Protons = Number of Electrons
       • Neutral Neutrons
       • Overall positive charge

2. Periodic Table

   • Columns
     • These are called Groups
       • Each Group have the same number of Electrons in their outer shell
         • Therefore the properties are similar
       • Group 0 are Noble Gases
         • This means they have a full outer shell
           • They are stable and unreactive
   • Numbers
     • The top number is the Mass Number
       • Number of Protons & Neutrons
     • Bottom number is the Atomic Number
       • Number of Electrons
     • To find the Neutrons it's Mass Number - Atomic Number

3. Electron Shells

   • Rules
     • Electrons occupy shells
     • There are usually 3 shells
       • First - 2 Electrons
       • Second - 8 Electrons
       • Third - 8 Electrons
     • A full outer shell means the Element is unreactive
       • Unless full the Element will react
   • Carbon Electron Shells
     • 2 electrons on first shell
     • 4 electrons on outer shell

4. Compounds

   • Formed
     • Different Elements react forming Chemical Bonds
       • Forms a Compund
       • Making Bonds involves taking and sharing Electrons
   • Bonding
     • Ionic Bonding
       • Occurs when metals and non-metals bond
         • Consists of Ions
       • The metal loses Electrons
         • Forms positive charge
       • The non-metal gains Electrons
         • Forms negative charge
       • The opposite charge causes the atoms to be attracted
         • Forms a compound
           • E.g. NaCl
             • Sodium Atom gives an electron to Chlorine Atom
     • Covalent Bonding
       • Occurs when two non-metals bond
         • Consists of Molecules
       • Each Atom shares an Electron
         • They have to share so they can have a full outer shell
           • Must have enough Covalent Bonds to do so
             • E.g HCl
               • The Hydrogen bonds with the Chlorine by sharing an Electron
   • Formulas
     • Carbon Dioxide
       • 1 Carbon Atom
       • 2 Oxygen Atoms
     • Calcium Hydroxide
       • 1 Calcium Atom
       • 2 Oxygen Atoms & 2 Hydrogen Atoms
         • These have brackets around them, with a little '2' next to it

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