A neutron is present inside the nucleus of an atom just like a proton with a basic difference that it does not have any charge like proton which has +1 charge. The mass of a neutron is almost equivalent to that of a proton which is approximately 1 a.m.u. The atomic mass of an atom is sum total of the mass of neutrons and protons present inside the nucleus of that atom.
But, atomic number of an atom is either equal to the number of protons or number of electrons present in that atom because in a neutral atom there are equal number of protons and electrons. Electrons do not have any mass so they only contribute to charge in the atom which is -1 for each electron.
With billions of moving particles colliding into each other, an area of high energy will slowly transfer across the material until thermal equilibrium is reached (the temperature is the same across the material).
"Compound: A substance that is made up of more than one type of atom bonded together.
Mixture: A combination of two or more elements or compounds which have not reacted to bond together; each part in the mixture retains its own properties."
