Ionic Bonds Flashcards
What affects melting points
Strength of electrostatic forces of attraction between oppositely-charged ions
(a) High boiling and melting points
Oppositely-charged ions are held tightly together by strong electrostatic forces of attraction in a giant ionic crystal lattice structure.
A large amount of energy is required to overcome these strong forces of electrostatic attractions between cations and anions.
(FYI) At room temperature -> insufficient energy from surroundins to overcome forces of attraction
What makes the melting point higher
Higher charge , smaller sized ions
(b) Hard and brittle
Hard : a large amount of energy is required to overcome the strong electrostatic attractions between anions and cations
Brittle : when a large enough force is applied, layers of ions can slide, bringing ions of like charges next to each other. These ions of like charges repel each other and the ionic lattice shatters.
(c) Conducts electricity in molten and aqueous states but non-conducting in solid state
Solid : ions are held in fixed positions in a giant ionic crystal lattice structure by strong forces of attraction. Ions are unable to move freely to conduct electricity and there is an absence of mobile charge carriers.
Molten : the ions are mobile and will migrate to the electrodes when a potential difference is applied. There is a presence of mobile charge carriers.
(d) Generally soluble in polar solvents such as water and insoluble in non-polar solvents such as hexane
Polar : possibility of forming forces of attraction
Non-polar : no effective interactions between ions and the molecules of non-polar solvents
Dissolving an ionic compound in water
Water molecules are attracted to ions in the giant ionic crystal lattice. The partially negatively-charged oxygen atoms of water molecules are attracted towards the cations towards the cations of the ionic compound. The partially positively-charged hydrogen atoms of water molecules are attracted towards the anions of the ionic compound.
Water molecules detach the ions from the crystal lattice structure and hence breaks up the ionic bonds between ions.
Water molecules form a sheath around the cations and anions respectively.
