This is just a small thing, not even a story, that my friends and I came up with while pondering the Periodic Table and discussing the Dark Knight. Here's what happened.
Batmanium
Symbol: Bw
Atomic number: 180,000,000
Atomic mass: 210
Street names: "Dark Knight", "Liquid Ninja"
Properties
Color: pitch black
Malleability: non malleable, unbreakable, immovable, incorruptible
Luster: shiny outside, dull grey inside
Conductivity: high, especially in the head region *Note: electrocutes people who try to remove its mask
Reactivity: extremely high. Explodes on proximity to crime (radius 50 miles), seeking out culprit and dealing out justice
*Note: Batmanium ignores many laws (of physics), and possesses "dark" (negatively charged) neutrons which allow its proton count to be so much higher than its atomic mass.
Reacts with: Rd (Rachelium), Af (Alfredium), Lf (Foxium), Cg (Gordium), and J (Jokerum).
Discovered by: Robert Kane
Jokerum
Symbol: J
Street names: "Clown", "Clown Prince (of Crime)", "Chaos"
Atomic number: 120
Atomic mass: 175.67
Color: purple, green, white, and red
Luster: none-rather pasty
Malleability: none. Cannot break. An unstoppable force
Non-conductive
Very reactive, explosive
Reacts with: Hd (Dentium), Bw (Batmanium), Rd (Rachelium), Cg (Gordium), Gg (Gotham Gangsterum)
*Note: Combination of these two elements results in perpetual violent explosion until one or the other is removed or destroyed.