Chemistry Trivia Questions and Answers

Atomic numbers, chemical formulas, pH and the oddities of the periodic table: these chemistry trivia questions start with the classroom basics and finish with a few that trip up even keen quizzers. Each answer has a short explanation and a fun fact, so you'll know why the answer is right, not just which one it is.

7 questions · Every answer explained · Fact-checked October 2026

1. 1. What is the chemical formula for water?

   • A. CO2
   • B. H2O
   • C. O2
   • D. H2O2
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   B. H2O — Each water molecule is made of two hydrogen atoms bonded to one oxygen atom.

   Did you know? H2O2, one oxygen atom more, is hydrogen peroxide — a bleach, not a drink.

2. 2. At sea level, at what temperature does water boil?

   • A. 90 °C
   • B. 100 °C
   • C. 110 °C
   • D. 120 °C
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   B. 100 °C — At standard sea-level pressure, pure water boils at 100 °C (212 °F).

   Did you know? On top of Mount Everest, the lower air pressure lets water boil at around 70 °C.

3. 3. Which element has the atomic number 1?

   • A. Helium
   • B. Hydrogen
   • C. Oxygen
   • D. Carbon
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   B. Hydrogen — Hydrogen has a single proton in its nucleus, giving it atomic number 1.

   Did you know? Hydrogen is the most abundant element in the universe — about three-quarters of all ordinary matter by mass.

4. 4. What is the pH of pure water at 25 °C?

   • A. 0
   • B. 5
   • C. 7
   • D. 14
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   C. 7 — Pure water is neutral, with a pH of 7; lower values are acidic and higher values are alkaline.

   Did you know? The pH scale is logarithmic, so pH 5 is a hundred times more acidic than pH 7.

5. 5. Which noble gas glows red-orange in classic advertising signs?

   • A. Argon
   • B. Neon
   • C. Krypton
   • D. Xenon
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   B. Neon — Neon gives off a red-orange glow when electricity passes through it; other colours usually come from other gases or coated tubes.

   Did you know? Neon's name comes from the Greek 'neos', meaning 'new'.

6. 6. Which element is the most electronegative?

   • A. Oxygen
   • B. Chlorine
   • C. Fluorine
   • D. Nitrogen
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   C. Fluorine — Fluorine tops the Pauling scale at about 3.98, meaning it pulls on shared electrons harder than any other element.

   Did you know? It's so reactive that it can make even some noble gases, like xenon, form compounds.

7. 7. Which is the only metal that is liquid at standard room temperature?

   • A. Gallium
   • B. Caesium
   • C. Mercury
   • D. Bromine
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   C. Mercury — Mercury melts at about −39 °C; gallium and caesium only melt a little above room temperature, and bromine is a non-metal.

   Did you know? Its symbol, Hg, comes from the Latin 'hydrargyrum', meaning 'liquid silver'.