Periodic Table Quiz: 25 Questions, With a Worked Answer Key

Before you start: most quizzes test the wrong thing

Search for a periodic table quiz and you will find a dozen games that ask you to name all 118 elements against a clock. They are good fun and they measure one thing: recall.

What they do not do is tell you why an answer is right. Get tungsten wrong on a timed grid and you learn that you did not know tungsten. You do not learn that its symbol is W because of an older name for the mineral it came from, which is the thing that would make you remember it next time.

So this one is built the other way round. Fewer questions, an explanation attached to each, and no timer. Work through it on paper. The answer key starts after question 25.

Tier one: the symbols that catch people out

Eight questions. These are the symbols that do not match the English name of the element, which is exactly why they are the ones people lose marks on.

• 1. Which element has the symbol K?
• 2. Which element has the symbol Na?
• 3. Which element has the symbol Fe?
• 4. Which element has the symbol Au?
• 5. Which element has the symbol Pb?
• 6. Which element has the symbol W?
• 7. Which element has the symbol Sn?
• 8. Which element has the symbol Hg?

Tier two: how the table is put together

Nine questions on structure rather than recall. If you can answer these you can find your way around a table you have never seen before.

• 9. How many elements are on the modern periodic table?
• 10. What is the atomic number of carbon?
• 11. How many protons does an atom of oxygen have?
• 12. Which element has atomic number 1?
• 13. Two elements are liquid at room temperature. Which two?
• 14. How many elements are gases at room temperature? Is it 5, 8, 11 or 15?
• 15. Lithium, sodium, potassium and caesium belong to which family?
• 16. Fluorine, chlorine and bromine belong to which family?
• 17. Hydrogen sits at the top of the same column as lithium and sodium. Does that make it an alkali metal?

Tier three: trends and reasoning

Eight questions. These are the ones that separate memorising the table from reading it.

• 18. Which element is the most electronegative?
• 19. Moving left to right across period 2, from lithium to fluorine, does electronegativity rise or fall?
• 20. Moving down the alkali metals, from lithium to caesium, does the first ionisation energy rise or fall?
• 21. Which element has the electron configuration [Ne]3s1?
• 22. Silicon is not a metal and not quite a non-metal. What is it classed as?
• 23. Uranium sits in the block at the bottom of the table. What is that family called?
• 24. What oxidation state does oxygen almost always take in a compound?
• 25. Which of these four was discovered most recently: gold, iron, lead or technetium?

The answer key

Answers are drawn from the US National Institutes of Health element database. Where a number matters, the number is given so you can check the claim rather than take it on trust.

Tier one

1. Potassium. The symbol comes from kalium, an older name for the metal. Humphry Davy isolated it and named it potassium, after potash. Berzelius, who did not isolate it, preferred kalium as the better reflection of its origins, according to the Royal Society of Chemistry. English kept Davy's name; the symbol kept Berzelius's.

2. Sodium. Na comes from an older name for the element, while the English name comes from soda.

3. Iron. Fe, again from an older name that English did not keep.

4. Gold. Au, same pattern.

5. Lead. Pb, same pattern.

6. Tungsten. W, and this one is not Latin. It comes from wolfram, after the mineral wolframite. The English name is from Swedish, tung sten, meaning heavy stone. So the name and the symbol come from two different languages, which is why it feels arbitrary.

7. Tin. Sn, same pattern.

8. Mercury. Hg. It is also one of the two answers to question 13.

The pattern worth taking away: when a symbol looks nothing like the element's English name, it is almost always because the symbol was fixed from an older name for the element and the English word went its own way. Potassium and tungsten are the two cases documented in the sources below; the others follow the same shape, and this piece does not put a specific older word in your mouth for elements it has not checked.

Tier two

9. 118. That is every element currently named on the table.

10. Six. Carbon's atomic number is 6.

11. Eight. Atomic number is the count of protons, and oxygen's atomic number is 8. That is the whole answer, and it is why question 10 and question 11 are really the same question asked twice.

12. Hydrogen. One proton.

13. Bromine and mercury. Exactly two, and this is a favourite exam question because most people get mercury and stop. Bromine is the one that gets forgotten.

14. Eleven. Hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon. The usual way to land short is to count the noble gases, remember oxygen and nitrogen, and then forget hydrogen, fluorine and chlorine. Those last three are the ones that get dropped.

15. The alkali metals.

16. The halogens.

17. No. This is the question in tier two that catches the most people, and the answer is a clean no. Hydrogen sits above the alkali metals because it has one electron, but it is classed as a non-metal. It behaves nothing like sodium or potassium: it is a gas, and it can gain an electron as well as lose one, which is why you see it with both a +1 and a -1 oxidation state. Position on the table and family membership are two different things, and hydrogen is the standing example.

Tier three

18. Fluorine, at 3.98 on the electronegativity values in the NIH dataset. For context, the next three are oxygen at 3.44, chlorine at 3.16 and nitrogen at 3.04. Fluorine is not just first, it is clear of the field.

19. It rises, and the run across period 2 is clean enough to quote in full: lithium 0.98, beryllium 1.57, boron 2.04, carbon 2.55, nitrogen 3.04, oxygen 3.44, fluorine 3.98. Every step up.

20. It falls. First ionisation energies down the alkali metals, in electron volts: lithium 5.392, sodium 5.139, potassium 4.341, rubidium 4.177, caesium 3.894. Every step down across those five. The outer electron sits further from the nucleus each time, so less energy pulls it away. One honest footnote: in this dataset francium, the next one down, comes in at 3.9, marginally above caesium, so the run is quoted as lithium to caesium rather than all the way to the bottom.

21. Sodium. [Ne]3s1 means a full neon core plus a single electron in the 3s orbital, and one loose outer electron is the signature of the alkali metals.

22. A metalloid. Silicon sits on the staircase between metals and non-metals and behaves like both, which is the property the whole semiconductor industry is built on.

23. The actinides. Uranium is an actinide.

24. Minus two. Oxygen's usual oxidation state is -2.

25. Technetium, in 1937. The other three are listed simply as ancient, because gold, iron and lead have been worked for thousands of years and nobody can date their discovery. Technetium is the interesting one for a different reason: it was the first element to be produced artificially.

What your wrong answers actually tell you

This is the part a scoring widget cannot do for you, and it matters more than the total.

Missing tier one is a vocabulary problem. Symbols are arbitrary labels and the fix is flashcards and repetition. It is annoying and it is not deep.

Missing tier two is a problem with how the table is organised, and it is worth taking seriously, because those questions are the ones that let you work out an answer you were never taught. A student who does not know that atomic number means proton count will keep meeting that gap.

Missing tier three usually means the trends were learned as sentences to recite rather than as consequences of structure. That is the most common shape of a chemistry problem in senior years, and it is also the most fixable, because the trends follow from a handful of ideas about distance from the nucleus and shielding.

And one thing that is not a knowledge problem at all: if your child can answer these at the kitchen table and then goes blank in a test, the difficulty is not the chemistry. We have written separately about why children freeze under test conditions and how to tell the two apart.

Where this sits in senior chemistry

If your child is deciding whether to take Grade 12 chemistry, or has taken it and is finding it harder than Grade 11 was, we have set out what SCH4U actually covers and what it assumes. There is a companion piece on Grade 12 biology with the same shape.

Where Genie fits

Genie works only with Canadian Certified Teachers, licensed by a provincial governing body such as the Ontario College of Teachers. Certification is verified before a teacher ever sees a student profile: the certificate number and issuing body are checked against the provincial registry, with a live government-ID match.

The reason that matters for a quiz like this one is in the section above. A wrong answer in tier one and a wrong answer in tier three are different problems, and telling them apart is the part a subject teacher does. A certified chemistry teacher also does not only work through the coursework in front of them: they can chart which courses a student needs for a particular programme later and aim the teaching at the areas that get them there. Parents get a per-lesson record of what was covered and what the child understood, so the picture builds week to week.

You can find a certified chemistry teacher here.