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The elements sodium to argon make up the third period of the Periodic Table - Scottish Highers Chemistry - Question 1 - 2017

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The elements sodium to argon make up the third period of the Periodic Table. Na Mg Al Si P S Cl Ar (a) Name the element from the third period that exists as... show full transcript

Worked Solution & Example Answer:The elements sodium to argon make up the third period of the Periodic Table - Scottish Highers Chemistry - Question 1 - 2017

Step 1

Name the element from the third period that exists as a covalent network.

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Answer

The element from the third period that exists as a covalent network is silicon.

Step 2

Explain why the first ionisation energy increases across the period.

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Answer

The first ionisation energy increases across the period due to the increasing nuclear charge. As more protons are added to the nucleus, the effective nuclear charge experienced by the outer electrons increases, which holds them more tightly and requires more energy to remove an electron.

Step 3

Write an equation, including state symbols, for the second ionisation energy of magnesium.

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Answer

The equation for the second ionisation energy of magnesium is:

extMg(g)Mg2+(g)+e ext{Mg} (g) \rightarrow \text{Mg}^{2+} (g) + e^-

Step 4

Explain why there is a large difference between the third and fourth ionisation energies.

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Answer

The large difference between the third and fourth ionisation energies can be explained by the removal of an electron from a more stable electron configuration. The third ionisation involves the removal of an electron from a 3s subshell, while the fourth involves removing an electron from a completely full outer shell, which is more energy-intensive due to increased stability.

Step 5

Explain fully, in terms of structure and the type of van der Waals forces present, why the boiling point of chlorine is higher than that of argon.

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Answer

Chlorine molecules (Cl₂) exhibit stronger van der Waals (London dispersion) forces compared to argon (Ar) atoms due to the larger number of electrons in Cl₂, which leads to greater polarizability. This enhances intermolecular attractions, resulting in a higher boiling point for chlorine compared to argon.

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