Read the rule before answering
Apply both conditions to the element: a one-letter official symbol and atomic number at most 30. A full name can be accepted even when the name itself has many letters.
Six untimed questions, starting with this one.
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Check this question’s accepted set without submitting to a game or opening the full answer list.
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Read the lesson — reveals answers & strategy
Understand the boundary
An element must have a one-letter chemical symbol and atomic number no greater than 30. A valid full name remains acceptable even when it has many letters. Conversely, a one-letter input cannot bring an out-of-range element into the set.
Verify the facts: IUPAC · Periodic table ↗
Choose an answer for your goal
Boron earns 72 points and accepts B, while fluorine earns 74 and accepts F. Vanadium accepts V and earns 94. Learn each symbol together with its element, then check the number boundary. Guessing a lone letter because it is fast creates avoidable failures; the value comes from knowing that the canonical answer qualifies.
Worked examples — reveals answers
- Boron · Accepted
- B has one letter and boron is inside the first 30 elements.
- Be · Outside this set
- Beryllium’s two-letter symbol fails the symbol-length test.
- I · Outside this set
- Iodine has a one-letter symbol but its atomic number exceeds 30.
Practice the distinction
Explain why boron passes and beryllium fails before checking either. Both fit the atomic-number range, but only one meets the symbol-length condition. Then check a symbol whose element is outside the range.
Try it in the checker ↑Give me a hint — no answer revealed
Start with the full category, then apply the exact boundary: Both conditions must match. Names and symbols accepted. You only need one qualifying answer. A longer name is not automatically rarer.
Reveal a verified practice pick
This pick belongs to the selected question’s answer set. Points are a fixed knowledge rating.
Reveal a fast high-scoring answer
Shortest accepted input at 65+ points
VVanadium · 94 points · 1 characters
Vanadium (V) has atomic number 23 on the IUPAC periodic table.
Highest fixed score
Vanadium94 points · Shortest accepted spelling: V
These are editorial points, separate from real player choice counts.
Reveal all 10 practice answers
Filter by a name or listed alias. Scores are fixed knowledge ratings.
10 accepted answers
No answers match these filters. Try another spelling or a lower minimum score.
What players actually choose
– UTC · 579 recorded daily rounds. Source: Krillionio daily submissions. Skips and timeouts are included in the denominator; practice and Battle are excluded.
362 / 579 rounds ended with an accepted answer (62.5%). Average: 25.4 fixed points.
Compare observed choices — reveals answers
Question quality signals
These measurements cover completed daily rounds recorded with timing and rejection details. Older rounds without those fields are excluded. At least 20 measured rounds are required per question.
Review thresholds: below 20% accepted, at least 40% timed out, or at least 30% of rounds with an unlisted input. These flags suggest checking the wording and answer coverage; they do not prove an answer is wrong or change points automatically. Abandoned rounds and practice attempts are not included.
How these statistics work
- What is counted
- Source: Krillionio daily submissions. Skips and timeouts count as rounds; practice and Battle are excluded.
- When comparisons appear
- A question needs at least 20 recorded rounds. An answer also needs at least 5 recorded choices within that question.
- What the data can tell you
- These anonymous browser records are not verified unique people or a representative survey. The player rarity index does not change game points or predict the original Krillion game. Raw submissions stay private.
Rule examples & common mix-ups — may reveal answers
- Both the element’s group and the atomic-number limit must fit. A chemical symbol is an accepted spelling, not a way to bypass either restriction.
These notes explain the question boundary; they are not a ranking of player mistakes.
Why these answers qualify
Each entry belongs to the bounded set defined by the prompt. The named source supports the underlying facts; our editorial scoring is a separate layer.
Source: IUPAC · Periodic table ↗
Reference version: 2026-09-13. See our answer policy for how we handle aliases and omissions.