C2 - Ionic Compounds Flashcards
What is the structure for ionic coumpounds called?
Ionic compounds have a structure called a giant ionic lattice. The ions form closely packed, regular lattice arrangement and they have very strong electrostatic forces of attraction between oppositely charged ions,in all directions of the lattice.
What is the structure of a single crystal of sodium chloride (table salt)
One giant ionic lattice. The Na+ and Cl- ions are held together in a regular lattice
(Check CGP 114 to see its structure in a diagram)
What do all ionic compounds have?
They all have high melting points and high boiling points due to the many strong bonds between the ions,It takes lots of energy to overcome this attraction
What happens when an ionic compound is solid?
The ions are held in place, so the compounds can’t conduct electricity.
What happens when ionic compounds melt?
The ions are free to move and they will carry an electric charge.
What happens when some ionic compounds dissolve in water?
The ions separate and are all free to move in the solution, so they will carry an electric charge.
How to work out the empirical formula of an ionic compound
1) If its a dot and cross diagram, count up how many atoms there are of each element.
Write this down to give you the empirical formula
2) If you are given a 3D diagram of the ionic lattice, use it to work out what ions are in the ionic compound
You’ll then have to balance the charges of the ions so that the overall charge on the compound is zero.
What is the empirical formula of potassium oxide?
The compound contains potassium oxide ions.Potassium is in group one, so it forms 1+ ions. Oxygen is in group 6 so it forms two minus ions. A potassium ion only has a one plus charge, so you need to have the balance of the two minus charge of an oxide ion. This means that the empirical formula is K2O
