Atomic Structure and Bonding

Atomic Structure and Bonding

1. Definitions

   • ATOM the smallest particle in an element
     • 3 particles protons , neutrons and electrons
     • protons=electrons
   • MOLECULE forms when 2 or more atoms are chemically joined
   • ELEMENT a pure substance that consists of only one type of atom it cant be broken by chemical means
   • COMPOUND a substance that consists of 2 or more elements chemically combinded
   • ATOMIC NO no of protons in the nucleus of an atom
   • MASS NO total no of protons and neutrons in an atom
   • RAM average mass of the atoms in an element compared to the mass of carbon 12
   • ISOTOPES atoms of the same element wjich have the same atomic no but different mass no= different no of electrons
   • DIATOMIC 2 atoms covalently bonded in a molecule
   • ALLOTROPES are different forms of the same element in the same physical state
   • ALLOY is mixture of 2 or more elements, at least one of which is metal, the resulting mixture has metalic properties

2. Atoms

   • +1electron-negative -1electron positive
     • no of neutrons= atomic no-mass no

3. Periodic table

4. Ionic bonding

   • form when a metal transfers electrons to a non metal producing positive and negative ions
   • is the attraction of oppositely charged ions in an ionic compound
   • Properties
     • crystalline solids
     • High melting and boiling points
       • electrostatic attraction attract positively charged ions
     • usually dissolve in water
     • dont conduct electricity unless molten or in a solution
       • this breaks the ionic lattice - ions are able to carry charge and move
   • metals lose e to form cations
   • non metals gain e to form anions

5. Covalent bonding

   • is formed by a shared pair of electrons
   • 2 non metals

6. Structure

   • Giant ionic lattice
     • Particles with opposite charges attract each other ELECTROSTATIC ATTRACTION
     • 3D network of positive and negative ions held together by ionic bonds
   • Giant covalent lattice
     • Diamond
       • each carbon atom is covalently bonded to 4 others
       • symmetrical tetrahedral arrangement
       • strong covalent bonds in all directions
       • hard to break apart
     • Graphite
       • layers of hexagonal rings
       • each carbon atom is covalently bonded to 3 others
       • carbon atom has a free electron which is donated to a cloud od delocalised electrons- able to conduct electricity
       • weak van der waals - able to slide over eachother easily
   • Molecular covalent
     • can be solids liquids or gasses
     • low melting and boiling points
       • weak van der waals
       • usually in soluble in water
       • do not conduct electricity
   • Giant metallic lattice
     • Packed tightly together
     • consist of positive ions surrounded by a sea of moving electrons
     • - e attract ALL + ions AND CEMENTS EVERYTHING TO GETHER

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