2.1 Periodicity

Figure 1 below shows the successive ionisation energies for a period 2 element.

Figure 1

With reference to electronic structures, state the identity of this element and explain your answer.

This question is about the elements which have atomic numbers 33 to 37.

The first ionisation energies of these elements are shown in Table 1.

Table 1

The trend in melting points across period 3 can be broken down as follows:

Elements 1 to 3: General increase

Elements 4 to 8: General decrease

Explain this trend in melting point across the Period 3 elements.

This question is about hydrogen, the element with atomic number Z = 1.

Hydrogen can be placed in several different positions in periodic tables. One is immediately above lithium in Group 1. Another is in the centre of the first row, as shown in the AQA Data Sheet.

Evaluate the position of hydrogen when it is placed immediately above lithium and state one reason in favour and two against.

This question is about Period 4 of the Periodic Table.

The first ionisation energies of the elements H to K are shown below in Figure 1.

Figure 1

State and explain the trend in first ionisation energies shown by the elements with the atomic numbers 2, 10 and 18.

The melting points of period 2 elements are shown in Table 1 below.

Table 1

Explain the trend in melting temperatures across the elements of Period 2 in terms of their structure and bonding.

Electrons in atoms occupy orbitals.

Figure 2 shows the first ionisation energies for six consecutive elements labelled A–F. 

Figure 2

The sequence of the first three elements in the Periodic Table is hydrogen, helium and then lithium.

Explain why the first ionisation energy of hydrogen is less than that of helium, but greater than that of lithium.

Compound J reacts with chlorine. The first five successive ionisation energies for an element J, are shown in Table 1.

Table 1

State the formula of the compound when element J reacts with chlorine.

This question looks at the trends across a period in the periodic table. Four sequences of elements across period 3 are shown below:

Na, Mg, Al                   Al, Si, P                       Si, P, S                                    P, S, Cl

Nitrogen is a period 2 element that exists as a diatomic molecule. The first to third ionisation energies, in kJ mol^-1, of nitrogen are 1402, 2856 and 4578.

Table 1 below shows the successive ionisation energies of an unknown element, X. 

Table 1

Deduce the period and identity of element X and explain your answer with reference to its electron configuration.

First ionisation energies decrease down groups in the Periodic Table.

Explain this trend and the effect on the reactivity of groups containing metals.

The ionisation energy values show a general increase across period 4 from gallium to krypton.

The ionisation energies of sodium, Na, are shown in Table 2 below.

Table 2

Show with a cross (x), in the third row of the table below, all the ionisation numbers that involve the removal of an electron from an s-orbital.

All elements have a value for a first ionisation energy. The first ionisation energy for all the elements is found in chemistry data books.

The table below shows successive ionisation energies of an element A, found in Period 3 of the Periodic Table.

Table 1

Identify element A.

Explain your answer using data from Table 1. 

The graph below in Figure 1 shows some information on the elements of Period 3 of the Periodic Table. 

Figure 1

State and explain the trend that this graph shows, including why there are values that deviate from the trend.

Explain why the second ionisation energy of aluminium is a larger value than the first ionisation energy.

Properties of elements in the Periodic Table can be predicted based on the element’s position, and various trends in properties are shown across the periods and down the groups of the Periodic Table. 

State and explain the trend in the atomic radii of the elements seen across Period 3.

Another property which shows a trend across a period of the Periodic Table is the melting point of a substance.

Explain why the melting point of sodium is lower than that of magnesium.

Explain how sodium conducts electricity.

Explain why the melting point of phosphorus (P₄) is lower than the melting point of sulfur (S₈). 

The Periodic Table is constructed in groups and rows of elements, and there are a number of periodic trends which can be seen.

Identify the element, from silicon to chlorine, that has the largest atomic radius.

Explain your answer.

Another property which shows a trend across a period of the Periodic Table is first ionisation energy. 

Figure 1

On the axes above, sketch a graph to show the trend in first ionisation energy across Period 2 of the Periodic Table. 

Write an equation for the reaction that occurs when the third ionisation energy of silicon is measured.

Explain why the value of the third ionisation energy of silicon is higher than the value of the second ionisation energy of silicon.

The atoms of metal elements from the Periodic Table will lose electrons to form positive metal ions. Different ions have different sizes.

State which of Mg²⁺ and Al³⁺ is the larger ion. Explain your answer.

The following table shows some successive ionisation energies of an element in Period 3 of the Periodic Table. 

Table 1

Identify this Period 3 element and state the equation for the final ionisation energy which will take place. 

Explain how successive ionisation energies demonstrate the existence of electron shells within atoms.

Use Table 1 to fully justify your answer. 

Give the meaning of the term 'periodicity'.

Include in your answer reference to the atomic radii of the Period 2 and Period 3 elements.

Specific values of atomic radii are not required.