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.