1.1. Period 3 elements all form oxides when they are reacted with oxygen.

Give an equation and two observations when magnesium is heated in oxygen.

1.2. Sulfur is another Period 3 element which will burn in air.  Give an equation and two observations for this reaction. 

1.3. The melting points of the highest oxides of some of the elements in Period 3 are given in Table 1. 

Table 1

i) Explain the decrease in melting point from phosphorus (v) oxide to sulfur trioxide.

ii) Explain why magnesium oxide has a higher melting point than sodium oxide.

1.4. Explain why magnesium oxide forms a weakly alkaline solution when it reacts with water.