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Bonding and Structure

To be revealed soon

Specification:

The bonding in giant lattice (metallic, ionic, covalent network) and simple molecular structure types; the typical physical properties (melting point, solubility in water, electrical conductivity) characteristic of these structure type.

Ionic bonding:

  • Ionic bonding is the electrostatic attraction between positive and negative ions in ionic compounds.

  • Ionic bonding is represented using dot and cross diagrams which show the outer shell electron movement.

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For example Sodium chloride

  • Sodium loses one electron from its outer shell hence having a charge of +1.

  • Chlorine has 7 electrons in its outer shell.

  • Chlorine gains one electron from the sodium hence has a charge of -1. 

  • Therefore, the formula is NaCl. 

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Physical Properties of Ionic compounds:

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Melting and boiling points:

  • There are strong electrostatic forces of attraction between oppositely charged ions in the giant ionic lattice. 

  • This requires a lot of energy and high temperatures to break the electrostatic attraction between the ions.

  • Therefore, it has a high melting and boiling point.

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Solubility Rules:

  • Tends to dissolve in polar solvents such as water.

  • All compounds of Group 1 and ammonia are soluble

  • All nitrates are soluble

  •  Ba , Ca  , Pb  , Ag  sulphates are insoluble

  • Ag  , Pb   halides are insoluble 

 

Electrical conductivity:

  • Ionic compounds will only conduct electricity if it is in either molten or aqueous state.

  • This is because the ions are free to move when molten/aqueous.

  • Ionic compounds do not conduct electricity in the solid state

 

Metallic bonding:

  • Metallic bonding is the strong electrostatic attraction of positive ions to the ‘sea of delocalized electrons. 

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Properties of Metals: Giant metallic lattice

  • They are malleable because the layers can slide over each other.

  • High electrical conductivity in both solid and liquid states because delocalized electrons can move.

  • High melting and boiling points.

  • Reactive metals react with water.

 

Covalent bonding:

  • Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.

  • Mostly occurs in molecules when there are 2 non-metals bonded together.

 

The covalent bond:

  • A covalent bond is the overlap of atomic orbitals each containing an electron.

  • Electrons are shared.

  • The full structural formula shows the relative positioning of atoms and the bonds between them as lines.

  • Unpaired electrons = lone pairs.

  • Multiple covalent bonds exist when 2 atoms share more than one pair of electrons. (E.g., O=O) . 

  • Double bond = the electrostatic attraction between 2 shared pairs of electrons and the nuclei of the bonding atoms.

  • Triple covalent bonds = the electrostatic attraction is between 3 shared pairs of electrons and the nuclei of the bonding atoms. For example Nitrogen.


 

Dative covalent bonds/coordinate bonds:

  • Dative covalent bonds mean that both electrons in a covalent bond come from the same atom.

 

For example: Ammonium ion 

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  • As you can see in the figure above, the nitrogen has used its lone pair of electrons to form a dative covalent bond to the H  ion. This is because the H  ion does not contain any electrons hence forms a dative covalent bond with Ammonia.

  • The dative covalent bond is represented using a double headed arrow with the head showing where the electrons are going to.

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Properties of Simple covalent structures:

  • Made of small molecules e.g., water, carbon dioxide.

  • Low melting and boiling points – weak intermolecular bonds break when heat energy is applied. Covalent bonds do not break!

  • Simple molecular substances do not conduct electricity.

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Properties of Giant covalent Lattice:

  • Occurs in non-metals of only but not limited to Boron, Carbon and Silicon.

  • High melting and boiling points = strong covalent bonds = requires a lot of energy to break.

  • Insoluble in almost all solvents.

  • Do not conduct electricity unless they are graphite or graphene.

  • Graphene and Graphite are both able to conduct electricity because they have delocalised electrons present within its structure.

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Written by :Bansari Sanghvi

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Study Tip:

*Elements in Group 15 have 1 lone pair of electrons

*Elements in Group 16 have 2 lone pairs

*Elements in Group 17 have 3 lone pairs

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