Bonding 1 - Ionic

Question 1

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What is ionic bonding?

Answer 1

The electrostatic attraction between oppositely charged positive cations and negative anions. It is usually formed by electron transfer from a metal atom to a non metal

Question 2

What affects the strength of an ionic bond?

Answer 2

• Charge of the ions
  ions with greater charge have greater attraction to other ions, forming a greater force of attraction
• The radius of the ions involved
  ions with greater atomic radius have a weaker attraction to the oppositely charged ion because the attractive forces have to act over a greater distance

Question 3

How do ions form

Answer 3

positive cat(ions) form from losing electrons
negative an(ions) form from gaining electrons

Question 4

Reasons for the trends in ionic radii down a group

Answer 4

Why do cations and anions increase in radius going down a group?
Greater number of shells, smaller attraction
* Increased shielding from complete inner shells
* Larger distance bertween nucleus and outer electrons

Question 5

Reasons for the trends in ionic radii for a set of isoelectronic ions, e.g. N<sup>3-</sup> to Al<sup>3+</sup>

Answer 5

From N<sup>3-</sup> to Al<sup>3+</sup> ionic radius decreases
* Same number of electrons, so electronic structure
* Increasing nuclear charge, resulting in greater nuclear attraction
* Stronger pull on the same number of electrons means the ions get progressively smaller as the electron cloud is pulled closer to the nucleus

Question 6

Physical properties of ionic compounds: melting points

Answer 6

• Strong electrostatic forces of attraction between oppositely charged ions
• Require large amounts of energy to overcome
• Also many of these bonds to break (giant lattice)

Question 7

Physical properties of ionic compounds: Brittleness

Answer 7

• Strong bonds between positive and negatve ions create crystals in rigid, lattice structures

Question 8

Physical properties of ionic compounds: solubility in water

Answer 8

• The positive cation from the ionic solid is attracted to the negative end of the water molecule (oxygen)
• The negative anion from the ionic solid is attracted to the positive end of the water molecule (hydrogen)

Question 9

Physical properties of ionic compounds: conduction

Answer 9

• Can only conduct electricity in a molten/dissolved state as the ions of the compound can move and carry charge
• Cannot conduct electricity as a solid because ions are fixed in place and unable to carry charge

Question 10

How do the migration of ions provide evidence for the existance of ions?

Answer 10

When an ionic compound undergoes electrolysis the postitive cation is attracted to the negative electrode (cathode) and the negative anion to the positive electrode (anode)

Question 11

Why is water chosen as a solvent for ionic compounds?

Answer 11

Because it is a polar molecule, meaning different ends of the molecule are oppositely charged and can react with the oppositely charged ions in an ionic compound

Question 12

Ionic equations and spectator ions

Answer 12

When writing an ionic equation, you only include the ions which actually take part in the reaction to form precipitates, elements, gas molecules, and liquid molecules

steps for writing ionic equations:
1. write down the balanced equation with state symbols
2. convert those chemicals that are ions in solution (aq) into their ions
3. cross out those ions that appear on both sides of the equation
4. check that the atoms and the charges balance

Question 13

Ionic equations for precipitation reactions

Answer 13

In precipiation reactions:
1. Nitrate(V) ions are never involved (soluble)
2. Group 1 ions are never involved (soluble)
3. Look for a precipitate forming (formed from oppositely charged ions reacting to form an uncharged insoluble solid)
4. Coloured precipitates usually either have a transition metal cation or the anion contains a transition metal

Question 14

Ionic equations for displacement (redox) reactions

Question 15

Reactions of acids