2.1 Ionic Bonding

What is an ionic bond?

Cations and Anions are electrostatically attracted to eachother because of opposite charges, usually between a metal and non-metal.

Isoelectronic:

2 different species with the same electron configurations

What are the 2 main points about metals?

1. Have a low ionisation energy

2. Have a low electronegativity energy

What are the 2 main points about non-metals?

1. Have a high ionisation energy

2. Have a high electronegativity energy

When does an ionic bond form?

When the difference in electronegativity between the two reacting elements is greater than 1.8

What is electronegativity measured in?

Pauling Scale

What are 7 properties of ionic bonds?

1. Usually form crystalline structures

2. High melting and boiling points (non volitaile)

3. Doesn't conduct electricity in solid state

4. Hard

5. Brittle

6. Usually soluable

7. Can conduct electricity in liquid state

What does the structural property of having a 'hard surface' reveal about an ionic bond?

It means that the ions are held together strongly and are not able to move - thus making them resistant to physical change

What does the structural property of 'not being able to conduct electricity in a solid state' reveal about an ionic bond?

• in an ionic lattice, the ions cannot move because they are fixed in a regular arrangement

• when heated- lattice structure breaks down- bonds are weakend- ions can move

• when dissolves- ions can move

Why is an ionic substance usually water soluble?

• water molecules are polar

• therefore they can squeeze in between the ions and disrupt the lattice

• forming a hydration shell

why don’t all ionic compounds dissolve in water?

• only those with an electrostatsic atttraction between the cations and anions WEAKER than the association between the ions and the partial charges of water molecules

What does the structural property of 'being brittle' reveal about an ionic bond?

• An atom arrangement is fixed,

• therefore when a force is applied the lattice will shift and like forces can come into contact

• - resulting in the lattice shattering

What is the definition of the 'empirical formula'?

It is the smallest whole number ratio of cation to anion, when all charges are balanced

Binary ionic compound:

composed of a metal cation and a non-metal anion

Ammonium ion:

NH₄⁺

Hydroxide ion:

OH-

Nitrate ion:

NO₃^–

Hydrogen carbonate:

HCO₃^–

Sulfate:

SO₄^2–

Phosphate:

PO₄^3–

Carbonate:

CO₃^2–

Redox reaction equations for 2Na+ Cl2 → 2NaCl

• 2Na → 2Na+ +2e-

• Cl2 + 2e- → 2Cl-

Transition element:

• an elemnt with a partially filled D sublevel

• these can form multiple ions with different charges

Lattice Enthalpy:

• the standard enthalpy change that ocucrs on the formation of gaseous ions from one mole of the solid lattice

how strong the ionic bonds are in particular ionic lattice

if the lattice enthalpy is postive the reaction is…

endothermic

Factors that affect lattice enthalpy:

• increases with ionic charge

• decrases with ionic radius

What are the solubility rules?

• SPAN: Sodium, Potassium, Nitrate and Ammonium SOLUBLE

• Chlorided SOLUBLE…except Silver and Lead(II)

• Sulphates SOLUBLE…except Barium, Calcium and Lead (II)

• Carbonates INSOLUBLE

• Hydroxides INSOLUBLE…Calcium slightly…