Calcium (element)
鈣 is a chemical element kanji specifically for calcium. Its meaning is narrowly tied to the element itself, with no broader conceptual extensions.
鈣 is a modern coined character for the element calcium. It combines the metal radical 金 with 丐, which likely contributes the phonetic value カイ.
The metal radical 金 signals a metallic element. The right side 丐 looks like a person begging for strong bones—calcium is what they need.
For カイ, imagine a calcium tablet shaped like a small kayak: kayak -> カイ, and the metal element keeps your bones strong.