Category Nuances for rubidium:

• heavy,
• rare,
• metallic,
• useful,
• larger,
• exotic,
• volatile,
• pure,
• corrosive,
• minor,
• inert,
• reactive,
• radioactive,
• real,
• electropositive,
• alkaline,
• atomic,
• fluid,

Simple Categories for rubidium:

• element,
• system,
• material,
• atom,
• metal,
• component,