Having looked into neutrinos and the process in which they were found I've started looking more in Wolfgang Pauli himself. I've read into this principle but there are a few things I would like to clear up. I have picked out the information I am interested in learning abou. "The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925. It states that no two identical fermions may occupy the same quantum state simultaneously. A more rigorous statement of this principle is that, for two identical fermions, the total wave function is anti-symmetric. For electrons in a single atom, it states that no two electrons can have the same four quantum numbers" - http://en.wikipedia.org/wiki/Pauli_exclusion_principle 1) These first few questions I am interested more in what the words in bold actually mean. A fermion is a particle with a half integer spin. I know that, but as a fact and do not have any reason to believe that other than I have found it on the internet. What does it mean by half integer spin? 2) What is a wave function, and what would make it anti-symetric? 3) What are quantum numbers? Thanks, any help would be great. I have looked on the wikipedia page but I sometimes get lost reading, as I am not working at a partciularly high level (AS Level) and this is not in the curriculum, but is just out of interest.