Atoms and Molecules Practice
Solve chapter-level practice questions for Atoms and Molecules with reveal-only solutions and quick revision support.
Practice Test 1
Laws of combination and atom-molecule basics.
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Practice Test 2
Valency, ions, and writing chemical formulae.
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Practice Test 3
Atomic mass and molecular mass applications.
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Practice Test 4
Mole concept and mixed chapter revision.
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Quick Q&A Before You Revise
Why do we need the mole concept at all?
Because atoms and molecules are far too tiny to count directly. The mole gives a practical bridge between laboratory mass in grams and the number of particles present.
What is the easiest way to write chemical formulae correctly?
Write the ions with their valencies first, cross the valencies, simplify if needed, and then check that the final formula is electrically neutral.
Why is water written as H2O and not HO?
Because hydrogen has valency 1 and oxygen has valency 2, so two hydrogen atoms are needed to combine properly with one oxygen atom.