Review Sheet – Bonding
When bonds form energy is released. When bonds are broken energy is absorbed.
A metal and nonmetal form an ionic bond
A difference in electronegativity of 1.7 or greater indicates an ionic bond
Ionic bonds transfer electons
Ionic substances are hard, have high melting and boiling points and conduct electricity in
the liquid state.
Covalent bonds are made from two non metals
A difference in electronegativity of less than 1.7 indicates a covalent bond.
Covalent bonds share electrons
Covalent bonded elements form molecular substances
Molecular solids are soft, have low melting and boiling points, and are poor conductors
of electricity
Each covalent bond contains a pair (2) shared electrons.
A Double bond has 2 pairs (4) of shared electrons. O2 has a double bond
A Triple bond has 3 pairs (6) of shared electrons. N2 has a triple bond
Non polar bonds are found in diatomic molecules
Polar covalent bonds are found when any two different non metals share electrons.
The degree of polarity is calculated by subtracting the two elements electronegativities.
The side with the element of higher electronegativity is the negative side. (Oxygen in
H2O)
The greater the difference in electronegativity the more polar a bond is.
Metallic bonds are found in metals, they are sometimes described as positive ions
surrounded by a sea of electrons.
Metals conduct electricity because of free flowing or mobile electrons.
Metals have the highest melting and boiling points and are good conductors of electricity.
Polar molecules are asymmetrical (H2O). Non polar molecules are symmetrical (CO2).
Polar molecules form dipole-dipole bonding which are strong intermolecular forces.
Hydrogen bonds are a strong form of dipole-dipole which occurs between compounds
containing Hydrogen and Fluorine, Oxygen, or Nitrogen.
The high boiling point of water is due to Hydrogen bonds.
Van der Waals forces are weak intermolecular forces between non polar molecules.
Strong intermolecular forces result in high boiling points.
Weak intermolecular forces result in low boiling points.
Molecular-Ion attraction occurs between polar solvents (like water) and ionic solids.