AQA · Chemistry · 8462
GCSE Chemistry (AQA): Covalent Bonding
Topic 2 — Bonding, Structure & Properties of Matter. Generated from the caption track of Cognito's lesson video "GCSE Chemistry - Covalent Bonding - Formation | Drawing Covalent Bonds (2027/28 exams)"; each card deep-links to the moment in the video it came from. Lesson 2.04 of Cognito's AQA GCSE Combined Science (Trilogy) and Chemistry course (Higher tier), filed under AQA Chemistry 8462. Teaching by Cognito — https://cognitoedu.org/coursesubtopic/c2-gcse-aqa-h-c_2.04.
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What is the main limitation of a displayed formula?
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It shows nothing about the 3D shape of the molecule.
What is the molecular formula of methane?
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CH4.
In a dot and cross diagram, why are dots and crosses used?
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So you can tell which atom each shared electron originally came from — one atom's electrons are dots, the other's are crosses.
What name is given to the repeating units that make up a polymer?
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Monomers.
Which type of diagram shows how a molecule's atoms are arranged in three dimensions?
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A 3D model.
Why do two chlorine atoms share electrons rather than transfer them?
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Both are non-metals needing one extra electron, so transferring would leave one atom short; sharing gives both a full outer shell.
How many electrons can hydrogen's outer shell hold at most?
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Two — it is the first energy level, so hydrogen needs one extra electron to fill it.
Define a simple molecular substance.
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A substance made of small molecules whose atoms are joined by strong covalent bonds, with only weak intermolecular forces between the molecules.
How is a covalent bond represented in a displayed formula?
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As a line drawn between the chemical symbols of the two bonded atoms.
Give one advantage of a displayed formula over a dot and cross diagram.
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Large molecules (e.g. glucose) can be drawn quickly and simply, where a dot and cross diagram would be too complicated.
How many covalent bonds does nitrogen form in ammonia, and why?
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Three — its second shell holds up to eight electrons, so it needs three more to become full.
Why are giant covalent structures such as diamond very strong?
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All of their billions of atoms are joined by covalent bonds in a regular lattice.
What is a covalent bond?
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A bond formed when two atoms share a pair of electrons, so both achieve a full outer shell.
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