Period 3 chlorides, radius and prediction
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 3 practice questions, 5 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Salt that dissolves, and a liquid that smokes
- Structure of the chlorides
Read the transcript of the teaching part
Last time
Before we start: last time, in Rate of reaction, collision theory and the Boltzmann distribution, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Salt that dissolves, and a liquid that smokes
Sodium chloride dissolves quietly in water. Silicon tetrachloride, dropped in, reacts violently and fumes. Both are chlorides of Period 3 elements. The difference lies in their structure and bonding, and it lets us predict how other compounds will behave too.
Structure of the chlorides
Sodium chloride and magnesium chloride are giant ionic lattices. They are solids, with high melting points, and conduct when molten. Aluminium chloride has a lot of covalent character. It forms the dimer Al two Cl six as a vapour, held by coordinate bonds. Silicon tetrachloride, phosphorus chlorides and sulfur chlorides are simple molecular. They are liquids or low-melting solids, and do not conduct. PCl five is a solid at room temperature. SiCl four and PCl three are colourless liquids.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Chlorides of Period 3.
The whole chapter: Chemical Periodicity, Chemical Periodicity.
Chapter 9: The Periodic Table: Period 3
- Period 3 oxides and physical properties 7 min
- Period 3 chlorides, radius and prediction 7 min
Also for A Level Chemistry 9701
Which topics come up most in A Level Chemistry 9701 past papers, counted from every paper since 2004: Paper 2 topic frequency, Paper 4 topic frequency.