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All 10 Flashcards — Molecular shapes (VSEPR)
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Question
What does VSEPR stand for?
Answer
**V**alence **S**hell **E**lectron **P**air **R**epulsion.
Question
What is an electron domain?
Answer
Any group of electrons around the central atom — a single/double/triple **bond (each = 1 domain)** or a **lone pair**.
Question
Shape for 2 domains, 0 lone pairs?
Answer
**Linear**, 180° (e.g. CO_{2}, HCN).
Question
Shape for 3 domains, 0 lone pairs?
Answer
**Trigonal planar**, 120° (e.g. BF_{3}).
Question
Shape for 4 domains, 0 lone pairs?
Answer
**Tetrahedral**, 109.5° (e.g. CH_{4}).
Question
Shape for 3 bonds + 1 lone pair?
Answer
**Trigonal pyramidal**, ~107° (e.g. NH_{3}).
Question
Shape for 2 bonds + 2 lone pairs?
Answer
**Bent**, ~104.5° (e.g. H_{2}O).
Question
How do lone pairs affect bond angle?
Answer
Lone pairs repel **more** than bonding pairs, so they **reduce** the bond angle.
Question
Why is CO_{2} linear despite double bonds?
Answer
Each double bond is **one** electron domain; 2 domains, 0 lone pairs → linear, 180°.
Question
Order of bond angle: CH_{4}, NH_{3}, H_{2}O?
Answer
CH_{4} (109.5°) > NH_{3} (107°) > H_{2}O (104.5°) — angle falls as lone pairs increase.
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Full study notes for Molecular shapes (VSEPR)
Topic 2.2 hub
The covalent model
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