Periodicity of Physical Properties of the Elements in Period 3 (Cambridge (CIE) A Level Chemistry): Exam Questions

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. 

i) Define the term electronegativity. 

[2]

ii) Complete Fig. 3.2 to show how electronegativity changes along Period 3. 

Fig. 3.2

[1]

iii) Explain your answer to part (ii).

[2]

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

i) Define ionic radius. 

[1]

 ii) Explain how ionic radius differs between cations and anions in terms of the parent atoms. 

[4]

On Fig. 2.1, sketch a graph to show the trend in the ionic radius of successive elements in Period 3. 

Fig. 2.1

Explain the trend shown in part (b).

Table 3.1 shows the melting points and atomic radii of the elements in Period 3, Na to Cl.

Table 3.1

Explain the difference in melting point for the elements Na and Mg.

Explain why phosphorous has a lower melting point than sulfur.

Explain the trend in atomic radius shown in Table 3.1 in part (a)