Covalent Bonding

Question 1

What is a covalent bond?

Answer 1

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

Question 2

Dot and cross diagrams

Answer 2

• Used to show hoe electrons behave in a covalent bond.

- There can be single, multiple (double and triple) and dative covalent bonding.

Question 3

Dative covalent bonding

Answer 3

• In dative covalent bonding, one of the atoms provides both of the shared electrons.
• The shared pair of electrons was originally a lone pair.
  For example: NH4+
• NH3 (ammonia) donates lone pair to a H+ ion.
• Dative covalent bond in NH4+ is shows by a bond with an arrow from the Nitrogen to Hydrogen.

Question 4

Special cases

Answer 4

• Few compounds contain atoms with fewer than 8 electrons in their outer shell: Boron Trifluoride.
• Few compounds can use d-orbitals to ‘expand the octet’. This means they contain atoms with more than 8 electrons in outer shell: Sulfur Hexafluoride.

Question 5

Average bond enthalpy

Answer 5

• Average bond enthalpy is a measurement of covalent bond strength.
• Average bond enthalpy measures the energy needed to break a covalent bond.