1. P, Q, R, X, Y and Z are consecutive elements of the Periodic Table. The table below shows the formulae of the oxide compounds of these elements.
(a) In which Group of the Periodic Table would you expect to find
(i) element P : ______________________________________
(ii) element Y : ______________________________________
(iii) element Z : _____________________________________
(b) What is the formula of the compound formed between the elements
P and X?
(c) Which of the oxide in the table above is an ionic compound? Give a reason for your answer.
(d) Write a balanced chemical equation to show the reaction of element Z in air to form Z2O.
2. Silicon and carbon are both in Group IV of the Periodic Table.
(a) Draw a diagram of an atom of silicon showing how the electrons are arranged and the numbers of protons and neutrons in the nucleus.
(b) Both carbon and silicon form oxides in which the bonding between the atoms is covalent. Carbon dioxide has a simple molecular structure whereas silicon(IV) oxide (silicon dioxide) has a macromolecular structure.
(i) Draw a dot-and-cross diagram (showing only valence electrons) to show the bonding in a molecule of carbon dioxide.
(ii) The structure of silicon(IV) oxide is as drawn below
Silicon(IV) oxide is a solid whereas carbon dioxide is a gas.
Explain this difference in terms of the structures of the two oxides.
(iii) Does silicon(IV) oxide, conduct electricity?
Explain your answer with reference to its structure.
3. (a) The table below shows the number of electrons and neutrons for ions A2-, B+, C3- and D2+.
(i) State the nucleon number of the 4 ions.
(ii) Give the electronic configuration of D.
(iii) What is the formula of the compound formed between A and B?
(b) Some physical properties of iron, sulfur and iron (II) sulfide are shown in the table below.
(i) Do you expect iron (II) sulfide to conduct electricity in the liquid state? Give a reason for your answer.
(ii) Account for the difference in the electrical conductivity between iron and iron (II) sulfide in the solid state.
(iii) Explain, in terms of the structure and bonding, the difference in the melting points between sulfur and iron (II) sulfide.
(b) PX4 1
(c) Z2O (Z is also accepted)
Z is in group I of the periodic table and hence, a metal.
Metal combines with oxygen which is a non-metal to form ionic compound.
(d) 4 Z + O2 –> 2 Z2O
(b)(i) Yes, the ions are free to move in the liquid state.
(ii) In solid state, the iron(II) ions and sea of electrons are joined by metallic bonds. The delocalised electrons can conduct electricity.
Iron(ll) sulphide cannot conduct electricity in the solid state because the ions are not free to move in the ionic lattice.
(iii) Sulfur has low melting point because of the weak intermolecular forces between the molecules. thus lesser amount of energy is need to overcome these forces. 
lron(ll) sulﬁde has high melting point because it is an ionic compound with strong electrostatic forces between oppositely charged iron and sulﬁde ions thus larger amount of energy is needed to overcome these forces.