First 166 words of the document:
The atom nucleus
The nucleus of an atom is the very dense region,
consisting of nucleons (protons and neutrons), at the
center of an atom. Almost all of the mass in an atom is
made up from the protons and neutrons in the nucleus,
with a very small contribution from the orbiting
The nucleus takes up such a tiny proportion of the actual
size of the atom but makes up for most of the total
The nucleus of an atom consists of protons and neutrons
bound by the nuclear force.
Which chemical element an atom represents is
determined by the number of protons in the nucleus.
Each proton carries a single positive charge.
Nuclei are bound together by a strong force this is what
keeps a structure hard. This force is much weaker
between neutrons and protons because it is mostly
neutralized within them.