A neutron walks into a bar and asks the bartender: "How much for a beer?" The bartender says: "For you, no charge."
Two atoms are sitting in a bar. One says to the other,
"I think I've lost an electron." The other asks "Are you sure?"
to which the first replies "I'm positive."
A proton walks into a bar and asks for a glass of water. The bartender asks, "Are you sure you don't want beer?" The proton replies, "I'm positive!"