Bonding

Bonding

Ionic Bonding

For ionic bonding two elements bond by donating or receiving electrons. This type of bonding occurs only between a metal and a non-metal, whereby the metal loses an electron while the non-metal receives the electron, producing two ions.

An example of how to draw an ionic bond is as follows:

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In ionic compounds, there are no bonds, but there are a number of interactions. The size of the ions shows the number of possible interactions, and therefore the bigger the cation the higher the number of anions that it can support.

How to draw an ionic bond.

For NaCl, each Sodium ion is surrounded by 6 Chlorine ions while each chlorine ion is surrounded by 6 Sodium ions.

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For a bigger cation such as Caesium 8 chlorine atoms surround the cation while 8 Caesium ions surround the anion.

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Covalent Bonding

For covalent bonding, there are only sharing of electrons, and these types of bonds involve two non-metals, where the electronegativity of the two atoms is similar. Electronegativity is a term used to show how much the element would like to obtain an electron.

An example of how to draw a covalent bond is as follows:

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How to draw a covalent bond.

Electronegativity

Electronegativity is a measure of the attraction of an atom for electrons in a covalent bond.

Fluorine is the most electronegative atom, while Francium would be the least electronegative. The closer the electronegativity is the more covalent a compound is while I the electronegative difference is big, an ionic bond would be formed.

electronegativity

Intermediate Bonding

Although most compounds are either ionic or covalent there is also the possibility of intermediate bonding. These are compounds that contain atoms with a high charge to surface area ratio, such as Al3+, Be2+ and Li+. The charge: surface area is so big that it will actually polarise the electrons from an anion to form a partial covalent bond, hence the term intermediate bonding.

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bonding 6VSEPR

Valence Shell Electron Pair Repulsion Theory is a way how to draw the shape of hybridised molecules. The number of bonds and lone pairs are counted and the shapes depend on the total number of electron pairs in the molecule.

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Using VSEPR

Intermolecular bonding

Dipole-Dipole

Unsymmetrical molecules which have different electronegative atoms will form dipole-dipole interactions since these would be permanently charged. These interactions increase the boiling points of such compounds.

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Induced dipole – Induced dipole

In the cases where the molecule is either symmetrical or when the atoms have similar electronegativity temporary charges will be found on each individual atom since the electron are all the time moving. When both electrons from a bond are closer to an atom they will produce a partial negative charge, with the other atom being partially positive.

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Hydrogen Bonding

A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine.

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Metallic bonding

Both Ionic bonding and Covalent, are mostly found in compounds, with the exception of the diatomic molecules were covalent bonds are found in elements. Most elemental metals have got metallic bonds, which in reality is a sea of electrons keeping metal ions together. This occurs due to the fact that metals would like to lose an electron, in order to have a noble gas configuration, and this is possible if an electron is free to jump from one atom to another.

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Summary of Properties

After having a look at all of the different types of bonding, one can then analyse different properties for different compounds, which have a direct combination to the bonding between the atoms.

Ionic compounds

  • They have high melting points and boiling points.
  • These are crystalline in structure.
  • In solution they are conductive.
  • Dissolve in water and other polar substances.

Covalent compounds

  • Compounds tend to have low melting points and boiling points.
  • Compounds tend to be made up of small molecules.
  • They do not conduct heat or electricity.
  • These are insoluble with water.
  • Inorganic covalent compounds tend to have low densities.

Metallic elements

  • Very good conductors of heat and electricity.
  • Metals tend to be malleable and ductile.
  • They have high melting points.
  • These compounds tend to have high densities.

Questions on Bonding

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