Science Week Chemistry Joke-Day 1

In Australia this week, from the 13th of August to the 21st of August, is Science Week. All around the country there are special scientific events taking place. As I have previously mentioned it is also the Intenational Year of Chemistry and therefore I will be posting one chemistry joke per week. However as this week is so scientific I will try to post 1 chemistry/science related joke per day... ENJOY
So, a neutron walked into a bar and said "I’d like a beer, please."

After the bartender gave him one, he said "How much will that be?"

"For you?" said the bartender "No charge."