Edexcel A-Level Chemistry: Atomic Structure & Periodicity
6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
The melting points of the Period 3 elements do not change in a simple way from left to right. Selected values are shown below.
| Element | Na | Mg | Al | Si | P₄ | S₈ |
|---|---|---|---|---|---|---|
| Melting point / °C | 98 | 650 | 660 | 1414 | 44 | 115 |
Describe and explain the trend in melting point across this part of Period 3. Your answer should account for why the melting point rises from sodium to aluminium, why silicon has the highest melting point, and why phosphorus and sulfur have much lower melting points than silicon. Refer to structure, bonding and the particles that must be separated.
(6 marks)
A high-purity sample of element Q was analysed in a mass spectrometer, which resolved four isotopes. The relative isotopic mass and percentage abundance of each are shown below.
| Relative isotopic mass | Percentage abundance / % |
|---|---|
| 50 | 4.00 |
| 52 | 84.0 |
| 53 | 9.00 |
| 54 | 3.00 |
(a) Use the data to calculate the relative atomic mass of Q. Give your answer to two decimal places and hence identify element Q. (4 marks)
(b) The isotope of relative isotopic mass 53 is the only one of the four with an odd mass number. State the number of neutrons in one atom of this isotope, and explain why all four isotopes give a single set of chemical reactions. (2 marks)
(Element Q has 24 protons.)
The first five successive ionisation energies of an element T, which is in Period 3, are listed below.
| Ionisation | 1st | 2nd | 3rd | 4th | 5th |
|---|---|---|---|---|---|
| Ionisation energy / kJ mol⁻¹ | 738 | 1451 | 7733 | 10543 | 13630 |
(a) Using the data, deduce which group of the periodic table T belongs to. Justify your answer by referring to a specific feature of the data. (3 marks)
(b) State the identity of element T, and explain why the second ionisation energy is larger than the first. (2 marks)
A coal-fired power station releases flue gas that contains sulfur dioxide, an acidic Period 3 oxide. To remove it, the gas is passed through a wet scrubber containing a slurry of an alkali.
(a) Explain, in terms of its position in Period 3, why sulfur dioxide is an acidic oxide whereas the oxide of sodium (Na₂O) is basic. (2 marks)
(b) In one scrubber design the slurry contains sodium hydroxide. Write a balanced equation, including state symbols, for the reaction of sulfur dioxide gas with aqueous sodium hydroxide to form sodium sulfite and water. (2 marks)
(c) A different scrubber uses solid magnesium oxide. State one observation, in terms of acid-base behaviour, that shows magnesium oxide is basic. (1 mark)
Thionyl chloride fluoride, SOClF, is a reactive molecule used in research laboratories. It contains one S–O bond, one S–Cl bond and one S–F bond. Some Pauling electronegativity values are given below.
| Element | F | O | Cl | S |
|---|---|---|---|---|
| Pauling electronegativity | 4.0 | 3.4 | 3.2 | 2.6 |
(a) Calculate the electronegativity difference for each of the three sulfur-containing bonds and hence identify the most polar bond in SOClF. (2 marks)
(b) For the most polar bond, state which atom carries the partial negative charge and explain your reasoning. (2 marks)
The first ionisation energy is an important property of an element.
(a) State the definition of the first ionisation energy of an element. (1 mark)
(b) Write an equation, including state symbols, to represent the first ionisation of a calcium atom. (1 mark)
(c) State one factor that determines the size of the first ionisation energy of an atom. (1 mark)