bonding

• Types of bonding


  • Metallic
  • Ionic
  • Covalent
• Metallic bonding


  • Occurs in metals
  • Results from an electrostatic attraction between positively charged metal ions and a sea of delocalised (free) electrons
  • Metallic bonds are strong
  • Most metals are solids, Mercury is the only liquid metal
  • As electrons can move from metal ion to metal ion, metals conduct electricity
• Ionic bonding


  • Ionic bonds are the electrostatic forces of attraction between positive ions and negative ions
  • Ionic bonds are strong
  • Ionic compounds have a lattice structure
  • Ionic compounds dissolve in water, the lattice breaks up
  • Ionic compounds conduct electricity as a melt or a solution as the ions are free to move, but not as solids
  • Ionic compounds have high melting and boiling points, so they are solids at room temperature
  • The colour of an ionic compound comes from the ions present
• When an ionic compound is dissolved in water a solution called an electrolyte is formed
• Electrolytes conduct electricity as the ions are free to move
• Solutions of ionic compounds can be broken down using a process called electrolysis
• Electrolysis


  The breaking down of a compound using electricity
• Covalent bonding


  • A covalent bond is a shared pair of electrons between atoms
  • Atoms share electrons to gain a full, stable outer shell of electrons
  • The atoms are held together in a covalent bond by the electrostatic attraction between the positively charged nuclei of each atom and the negatively charged electrons
  • Covalent substances do not conduct electricity, except for carbon in the form of graphite
  • Most covalent substances do not dissolve in water, but some do dissolve in other substances like acetone
  • Covalent molecules tend to be liquids or gases at room temperature as they have low melting and boiling points
• Molecule


  A group of atoms held together by covalent bonds
• Diatomic molecule


  A molecule made up of two atoms
• Elements that exist as diatomic molecules

  • Hydrogen
  • Nitrogen
  • Oxygen
  • Fluorine
  • Chlorine
  • Bromine
  • Iodine
  • Astatine
• Diagrams can be drawn to show how the outer electrons in atoms are shared to form a covalent bond
• Shapes of molecules


  • Linear
  • Angular
  • Bent
  • Pyramidal
  • Tetrahedral
• Covalent networks


  • Covalent substances can also exist as giant networks
  • Examples are diamond (carbon) and sand (silicon dioxide)
  • They only contain strong covalent bonds and therefore are solids and have extremely high melting and boiling points
• Properties of covalent networks

  • Element present
  • Structure
  • Melting point (C)
  • Boiling point (C)
• Bonding summary


  • State at Room Temp
  • Type of Bonding
  • Conduction as a Solid
  • Conduction as a Liquid
  • Conduction as a Solution