Columbium (old element name), Niobium
鈳 is a rare kanji used for the chemical element niobium, formerly known as columbium. Its meaning is limited to this specific element name.
鈳 is a modern coined character for the element niobium. It combines the metal radical 金 with the phonetic component 可 (ka), which likely provides the on-reading カ. The character was created for scientific terminology and has no ancient origin.
The metal radical 金 hints at a metallic element. The right side 可 (possible) can remind you that this metal makes many alloys possible. Together, 鈳 is the metal niobium.
For ア, imagine a scientist saying 'Ah!' upon discovering niobium: 'Ah!' -> ア, the first sound of the element's old name columbium.