Chapter 5 - Electron Structure

ionic bonding

strong electrostatic forces of attraction holding the oppositely charged (positive and negative) ions together in all directions in a repeating/alternating pattern

PROPERTIES of giant ionic lattice -high melting + boiling points

has strong electrostatic forces of attraction between ions which require lots of heat energy to break

-poor electrical conductivity as solid + good as molten

ions cannot move around while in solid as they are fixed in place (no mobile charge carriers) but in liquid as the ions are able to freely move around and carry charge

-soluble in polar solvents e.g. water

ions in ionic compounds can interact with polar water molecules as they break down the ionic lattice and attract and surround the ions

covalent bond

strong electrostatic forces of attraction between a shared pair of electrons and the nuclei of the bonded atoms

PROPERTIES of simple covalent/molecular structure -very low boiling point

there are weak intermolecular forces between the atoms so very little heat energy needed to break

-poor electrical conductor

has no delocalised electrons and no ions (no mobile charge carriers) that are free to move around and carry charge

octet rule

when bonded atoms achieve 8 electrons on their outer shell in order to achieve stability when they bond to other atoms

EXCEPTIONS of octet rule

boron trifluoride (BF₃) - has 6 electrons on outer shell

sulfur hexafluoride (SF₆) - has 12 electrons on outer shell

phosphorus pentachloride (PCl₅) - has 10 electrons on outer shell

chlorine trifluoride (ClF₃) - has 10 electrons on outer shell

sulfur tetrafluoride (SF₄) - has 10 electrons on outer shell

dative covalent bond

type of covalent bond where one atom supplies both of the shared pair of electrons to the covalent bond

-use an arrow to show which atom is receiving the lone pair