Ionic Bonding
Ionic bonding is the electrostatic attraction between positive and negative ions
Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
Covalent bond is the overlap of atomic orbitals, each containing one electron to give a shared pair of electrons.
Displayed Formula
Double covalent bonds
Ionic bonding is the electrostatic attraction between positive and negative ions
- Structure
- The charged ions attract in all directions resulting in a giant ionic lattice which can contain many ions. An example would be a lattice of Na+ and Cl- in which each sodium ion is surrounded by 6 chlorine ions. Similarly chlorine ions are surround by 6 sodium ions.
- Melting / boiling point
- Most ionic compounds are solids at room temperature, at a low temperature there is not enough energy to overcome the attraction. Therefore high temperatures are needed to break the strong electrostatic forces of attraction. The melting point is higher for lattices with greater ionic charges.
- Solubility
- Most ionic compounds dissolve in polar solvents. This is because the water molecules surround the lattice. Some lattices with larger charges will not be soluble.
- Conductivity
- In solid state the ionic compound does not conduct electricity. In a solid the ions are in a fixed position and there are no charge carriers. In a liquid or aqueous state ions are free to move and carry charge.
Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
Covalent bond is the overlap of atomic orbitals, each containing one electron to give a shared pair of electrons.
- The shared pair of electrons is attracted to the nuclei of both the bonding atoms
- The bonded atoms often have outer shells with the same electron structure as the nearest noble gas (a full outer shell)
Displayed Formula
- A displayed formula shows the relative positioning of atoms and bonds between them as lines
- Paired electrons that are not shared are called lone pairs and are shown on the displayed formula
Double covalent bonds
- In a double bond the electrostatic attraction is between two shared pairs of electrons and the nuclei of the bonding atoms.
- In a triple bond, the electrostatic attraction is between three shared pairs of electrons and the nuclei of the bonding atoms
- A dative / coordinate bond is a covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only
- In a dative covalent bond the shared electron pair was originally a lone pair of electrons on one of the bonded atoms.
- In the case of Ammonia (NH3)
- An ammonia molecule donates its lone pair of electrons to a H+ ion
- The dative covalent bond in NH4+ is shown by a bond with an arrowhead to show the electron pair being donated to the other atom
- In an NH4+ ion, all four bonds are equivalent with no physical differences although it is displayed as an arrow instead of a line