An instructor in chemical warfare asked soldiers in his class: "Anyone knows the formula for water?"
"Sure. That's easy," said one man.
"What is it?"
"H, I, J, K, L, M, N, O."
"What, what?" reasked the instructor.
"H to O," explained the chemistry expert.
Did you check the news? There was a Radon the chemical store.
I like looking at a chart of all the chemical elements... periodically.