Remember that electronic structures may be written in the “GCSE” manner, in full or in a truncated manner.

Eg. ₁₉K “GCSE” 2.8.8.1

Full 1s² 2s² 2p⁶ 3s²3p⁶ 4s¹

Truncated [Ar] 4s¹

All three show K needs to lose 1 electron (OXIDATION) to have a full outside shell (Stable Octet). The truncated form shows that the resulting ion has the same electronic structure as Argon. The ion is positive – a Cation.

Oxidation K --> K⁺ + 1e^-

[Ar] 4s¹ --> [Ar]

#2

Eg. ₈O “GCSE” 2.6

Full 1s² 2s² 2p⁴

Truncated [He] 2p⁴

All three show O needs to gain 2 electrons (REDUCTION) to have a full outside shell (Stable Octet). The truncated form shows that the resulting ion has the same electronic structure as Helium. The ion is negative – an Anion.

Oxidation O + 2e^- --> O^2-

[He] 2p⁴--> [He]

Write truncated electronic structure for the following elements and show how they gain a full outside shell by either Oxidation or Reduction. State whether the resulting ion is an Anion or Cation

1. ₁₇Cl

2. ₂₀Ca

3. ₇N

4. ₁₂Mg

5. ₁₆S

6. ₉F

7. ₁₃Al

8. ₃Li

9. ₁₅P

10. ₁₁Na

Formulae of ions.

1. You can work out the charge of simple ions from Group 1,2,3,5, 6 & 7 from their position in the Periodic Table.

Grp 1 ₃Li (2.1) --> Li⁺ Grp 2 ₄Be (2.2) --> Be²⁺

₁₁Na (2.8.1) --> Na⁺ ₁₂Mg (2.8.2) --> Mg²⁺

₁₉K(2.8.81) --> K⁺ ₂₀Ca (2.8.8.2) -->Ca²⁺

Grp 3 ₁₃Al (2.8.3) -->Al³⁺

Grp 5 ₇N (2.5) --> N^3- Grp 6 ₈O (2.4) --> O^2-

Grp 7 ₉F (2.7) --> F^-

2. You can read the charge of simple ions from the Transition Block or Group 4 by looking at the Roman Numeral that accompanies them.

Fe(II) = Fe²⁺ Fe(III) = Fe³⁺ Pb(II) =Pb²⁺ Pb(IV) = Pb⁴⁺

3. You are expected to remember that Zinc is always Zn²⁺ and Silver is Ag⁺ and Hydrogen ions are H⁺.

4. You are expected to recall the names, charges and formulae of a few polyatomic ions

· Write formulae for the following ionic compounds

1. Potassium Hydroxide

2. Magnesium Sulphide

3. Copper(II) Carbonate

4. Aluminium Sulphide

5. Iron(III) Oxide

6. Sodium Carbonate

7. Aluminium Hydroxide

8. Ammonium Nitrate

9. Zinc Nitrate

10. Magnesium Carbonate

· You must learn the following properties of Ionic Compounds

1. High Melting/Boiling points

2. (Generally) Soluble in polar solvents (like water)

3. Insoluble in non-polar solvents (such as CCl₄)

4. Low Volatility (see point 1)

5. Electrical insulator when solid

6. Electrical conductor when molten or in solution

Now learn how to explain the above.

Q1. Using information from the table & your knowledge of the Periodic Table account for the differences in melting points between:

a) NaI and NaCl

b) NaBr and KBr

c) CaCl₂ and NaCl

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b_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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Q2 Suggest reasons why MgO has a much higher Melting Point than any other compound in the list

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Fundamentally, if ions can move charge can move.

And moving electric charge is a current.

· Why would a 1 mol dm^-3 solution of NaCl conduct less well than a 1 mol dm^-3 solution of (NH₄)₃PO₄ ?

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