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Course: High school chemistry > Unit 2

Lesson 2: Covalent bonds
Science
High school chemistry
Chemical bonding
Covalent bonds
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Apply: covalent bonds and molecules

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You might need: Periodic table

Problem

Caffeine is a central nervous system stimulant. It is present in coffee, cocoa, and some teas.
The Lewis structure of a caffeine molecule is shown below. One of the bonds has been replaced by a question mark (?).
A large molecule consisting of C, N, O, and H atoms connected by lines. A red question mark sits between an N and a C. The N atom is connected by a single line to a different C atom on the other side. The N has a pair of dots next to it. The C on the other side of the question mark is connected by a single line to a different N atom, and is also connected by a single line to an H atom.
Complete the statement.
The missing bond in the caffeine molecule is a ______.
Choose 1 answer: