CHEMISTRY

ATOMS AND IONS

Number of protons = number of electrons

Isotopes:  Different atomic forms of the same element, which have the SAME number of PROTONS but different number of NEUTRONS.

Ionic bonding = transferring electrons

Giant ionic structures have:

  • High melting and boiling points
  • Dissolve to form solutions that conduct electricity
  • They conduct electricity when molten

Cations  +

Anions  - 

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COVALENT BONDING

Simple molecular substances:

  • Form very strong covalent bonds to form small molecules
  • Force of attraction is very weak between the molecules
  • Most are gases or liquids at room temperature

 

DIAMOND

 

 

 

1 carbon = 4 covalent bonds forming a very hard and rigid structure

GRAPHITE

 

 

 

 

 

 

 

 

 

1 carbon = 3 covalent bonds forming layers that are free to slide over eachother. The layers are  loose so they can be rubbed off. Leaves free electrons - graphite is the only non-metal which is a good conductor of electricity

SILICA

Each grain of sand is one giant struture of silicon and oxygen, it can be melted down with sodium carbonate and limestone to make glass.

Giant covalent structures:

 

  • NO CHARGED IONS
  • Have very strong covalent bonds
  • Very high melting and boiling points
  • Don't conduct electricity, even when molten
  • Usually insoluble
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