Germanium (element)
鈤 is a rare kanji used specifically for the chemical element germanium. It has no broader conceptual center beyond this technical meaning.
鈤 is a modern kokuji created in Japan to represent the element germanium. It combines the metal radical 金 with 日, likely chosen for its phonetic value or as a simplified phonetic component.
The left side 金 (metal) and right side 日 (sun/day) together suggest a metal associated with the sun or daylight, helping recall that 鈤 is a metallic element.
For ジツ, imagine a scientist saying 'Jitsu!' when they discover germanium in a metal sample: Jitsu -> ジツ, and the metal 金 is the key.