Bonds and intermolecular forces

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  • Created on: 11-05-14 15:53
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Types of bonds
Ionic bonds:
An ionic bond is where metals and nonmetals bond. One atom donates an electron (becoming
a +1 ion) and the other accepts it (becoming a 1 ion). This difference in charge makes the two
atoms electrostatically attracted to each other, therefore forming an ionic bond.
Ionic compounds form an ionic lattice shape (like this!):
A good example of an ionic compound is sodium
chloride (NaCl).
Covalent bonds:
A covalent bond is where nonmetals bond together. They each share electrons from their outer
shell. This is the strongest type of bond, and so requires the most energy for it to be broken.
Covalent compounds have a giant covalent structures, and are called macromolecular.
Examples of covalent compounds include diamond and graphite, but these both have different
structures. Diamond has carbon atoms that form 4 bond with other carbon atoms so it is VERY
strong graphite forms 3 carboncarbon bonds and forms into layers that form van der Waals
forces between each other.
Metallic bonds:
This is a bond that only occurs in metals. Positive metal ions are surrounded by a sea of
delocalised electrons. The difference in charge between the electrons and the ions create strong
electrostatic attraction between the two. These atoms form into a lattice shape and the layers of
ions can slide over each other unless the metal is an alloy (this is what makes the metal
Coordinate bonds (also called dative bonds):
One atom donates both electrons to a vacant orbital of another atom to form a
covalent bond. This is drawn with an arrow rather than a line like a normal bond:
Intermolecular forces
Van der Waal forces (also called temporary/induced dipoledipole forces):
These are the weakest type of intermolecular force and occurs between all molecules. Electrons
are spread randomly in the orbitals and they can be at any particular point at any time. This
means that the electron density is likely to be more `concentrated' at one side of the atom or
molecule at once, therefore making it polar. The positive side of the molecule is attracted to the
negative side of another. This can induce the adjacent molecule to become polar too, causing a
domino effect. Because the distribution of electrons in an orbital is random, the van der Waal
forces are broken and made all the time.
The bigger the molecule, the stronger the van der Waal forces will be as the surface area of the
molecule has increased too. When a substance melts or boils it is the intermolecular forces that
break, not the bonds.

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Permanent dipoledipole forces:
The greater the difference in electronegativity between elements with covalent bonds, the
stronger the permanent dipoledipole forces will be. These are permanent (unlike van der Waal
forces) because they are due to the electronegativity of the elements, not the random chance of
electrons. When a substance melts or boils it is the intermolecular forces that break, not the
Hydrogen bonds:
These are the strongest type of intermolecular force.…read more


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