Limits RegistryPUBLIC RECORD
Limits RegistryCalcium (Ca) has atomic number 20, the number of protons in its nucleus.
The question, scope, and sources behind this Registry record.
Calcium (Ca) has atomic number 20, the number of protons in its nucleus.
Record the atomic number of Calcium.
This record identifies Calcium by its atomic number, an exact integer that defines the element. The value is independent of sample mass, isotope abundance, and chemical compound, while the cited periodic-table source provides the authoritative element identity.
NIST Periodic Table of the Elements — Calcium atomic numberChange a parameter to stress-test whether a proposed result is still inside the published specification. This is an audit aid, not a proof checker.
Current frontiers derived from accepted Claims.
The accepted equality closes this optimization result.
The frontier is not sacred
Most progress starts with a disagreement that survives contact with evidence. If you can push the known lower bound up or pull the upper bound down, show us the work.
≥ when you have shown that at least this value is achievable.≤ when you have shown that anything above this value is impossible.No vibes. State the value, define the scope, and link the paper, proof, code, or reproduction that lets another person check it. Editors review every challenge before the public record changes.
Challenge this recordAssertions tied to evidence, attribution, and review.
The frontier as it changed over time.
Only accepted Claims matching the current specification contribute to the displayed bounds. Strict inequalities remain open; contradictory Claims require editorial review.
limitsregistry.com/limits/LR-005019No active verified bounties are linked to this Limit.
View verified bounty tracker ↗No accepted machine-checked reproductions are recorded for this Limit.
Limits Registry. LR-005019. Calcium atomic number. 2026.