neutron

A subatomic particle which, with protons make up the nucleus of most atoms (hydrogen doesn't need to have any). They can spontaneously decay into a proton, electron, and a neutrino. Differing numbers of neutrons in an atom's nucleus determine what isotope it is. They have 0 electric charge as they are comprised of 1 up and 2 down quarks.

Neutron is a game for two players on a five-by-five board. The game starts with five white pieces on White's home row (one edge of the board), five black pieces on Black's home row, and the neutron in the center.

b b b b b
. . . . .
. . * . .
. . . . .
w w w w w 

• Pieces move in a straight line horizontally, vertically, or diagonally.
• Pieces must move as far as they can go in the chosen direction.
• Pieces can only move through or onto empty squares.
• There is no capturing.

Play begins with one player moving a piece from the home row. Thereafter on each turn, a player moves first the neutron and then one of his or her pieces.

The object of the game (any one will win)

• Move the neutron into your home row.
• Cause your opponent to move the neutron into your home row.
• Block the neutron completely so your opponent can't move it.

• Outside the nucleus, neutrons only live for about 10 seconds before decaying as mentioned above.
• Free neutrons (as in the 'unchained' sense) are valuable. They are a lot harder to get a hold of than electrons, alpha particles or even gamma rays, so any process that generates a stream of these particles is prized. Nuclear reactors are a common source of neutrons.
• It is neutron bombardment which transmutes a nucleus of one element to another. Electrons don't do it, and alpha particles need to be travelling pretty fast to do it.
• Because of the above properties, it is neutrons that are the most dangerous radiation of any radioactive material, as they are the most efficient at rendering neighbouring materials radioactive.
• Neutron capture is what causes a U-235 nucleus to fission and release more neutrons, precipitating a chain reaction.
• Upon release, neutrons in nuclear reactors travel too fast to be captured by uranium nuclei. They need to be slowed down by collisions with atoms in moderator materials, such as heavy water, graphite, or cadmium. They are much more likely to be captured by U nuclei once they have been slowed down in such a way.