The Periodic Table: Chemical Periodicity (CIE AS Chemistry)

The properties of elements and their compounds show similarities, differences and trends depending on the positions of the elements in the Periodic Table.

The positions of some elements are shown.

Fig. 1.1

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Fig. 1.2 shows the relative first ionisation energies of six successive elements in the Periodic Table.

The letters are not the symbols of the elements.

Fig. 1.2

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Fig. 1.3

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Oxides are compounds which usually contain oxygen combined with one other element.

Oxides are classified as follows.

Complete Table 2.1 to describe the oxides of the elements of the third period of the Periodic Table from sodium to sulfur.

Some of the oxides produced can react with water. 

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Give the oxidation number for the Period 3 element in each oxide.

The melting points of the two Period 3 oxides are displayed in Table 2.2. 

Explain the difference in melting points.

You should refer to the structure and bonding of each substance.

The elements in Period 3 of the Periodic Table show variations in their behaviour across the period.

Fig. 3.1 shows the variation of melting points of the elements across Period 3.

Fig. 3.1

In each of the following parts of this question you should clearly identify the interactions involved and, where appropriate, explain their relative magnitudes.

Explain the general increase in melting point from Na to Al.

Explain the variation of melting points from P to Ar.

Explain why Si has a much higher melting point than any of the other elements in the period.

Going across Period 3, a trend in electronegativity can also be observed. 

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This question concerns the chlorides of the elements sodium to phosphorus of the third period of the Periodic Table.

The melting points of these chlorides are given below in Table 4.1

Table 4.1

*sublimes at 451 K

Give the equation, with state symbols, for the reaction of phosphorus with chlorine to form phosphorus(V) chloride, PCl₅.

Suggest, in terms of the structure and bonding, explanations for the following.
You should draw diagrams where you think they will help your answer.
 

Write an equation for the reaction of silicon tetrachloride with water.

What is the pH of the solution formed when each of the following compounds is dissolved in water?

Elements in the same period of the Periodic Table show trends in physical and chemical properties. 

The ionic radius for the Period 3 elements are in Table 5.1 

Table 5.1

Complete Fig 5.1 to show the variation in ionic radius of Period 3 elements. 

Fig. 5.2

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Period 3 elements can react with oxygen to form oxides. 

Some Period 3 elements can react with water. 

In the boxes below write the formulae of one of the oxides of each of these five elements.

Explain why aluminium oxide is known as amphoteric. 

You should use equations in your answer. 

Sodium oxide and sulfur dioxide are separately added to water.

Write equations for and observations of each reaction and state the pH of any solution formed.

• Sodium oxide and water
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• Observations
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• Resulting pH
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• Sulfur dioxide and water
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• Observations
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• Resulting pH
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A concentrated solution of the compound produced when sodium oxide is added to water is heated with silicon dioxide.

Write the ionic equation for this reaction.

Compound A is an oxide of a Period 3 element. It dissolves in hot, concentrated potassium hydroxide and in nitric acid, but it is insoluble in water. 

The acid-base character of the Period 3 oxides changes from sodium to sulfur.

In terms of electronegativity of the Period 3 element, explain why the acid-base character changes.

When phosphorus(V) oxide reacts with water it will produce phosphoric acid. 

Phosphorus(V) pentoxide reacts with sodium hydroxide solution, NaOH (aq), to form a phosphate salt. 

Silicon(IV) chloride is formed by the reaction of silicon and chlorine.

The reaction of silicon(IV) chloride and water is very violent giving a white solid, silicon dioxide and steamy fumes of hydrogen chloride.

 
Tetrachloromethane gives no reaction with water.

 
Using your knowledge of electronic configuration, explain the difference between these two observations.