# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
N
net force: The sum of all the forces acting on an object.
neutralisation: The process where an acid is added to a base, or a base is added to an acid, to produce a neutral solution.
neutral substance: A substance that is neither an acid nor a base.
neutron: A subatomic particle that has no electric charge.
newton (N): A unit of force. 10 N is approximately equivalent to the squashing effect a 1 kg object has when placed on another object.
non-bonding electrons: Electrons that form pairs and fill orbitals in an atom and therefore do not take part in bonding.
non-Newtonian fluid: A substance that appears not to obey Newton’s laws of motion.
normal force: A contact force that acts perpendicularly to the surface of contact between two objects.
nova: A star that suddenly increases in brightness.
nuclear force: A field force that keeps the centre of an atom together.
nuclear reaction: A reaction that is attributed to changes in the nucleus of an atom.
nucleus: The small, very dense centre of an atom, composed of protons and neutrons.