The electron.
Mass number/Atomic Mass
The nucleus contains the mass.
the nucleus of the atom
Neutrons add mass and stability to an atom by increasing the atomic weight without changing the chemical properties. They also help to hold the nucleus together by balancing the repulsive forces between protons.
In the nucleus of the atom, protons and neutrons therein each add 1 atomic mass unit.
the nucleus
electron
The smallest part of an atom would be a quark. Quarks are either up or down quarks, and have virtually no mass. Neutrinos have even less mass, but are not part of an atom.
To the find the mass number of an atom you add the protons and neutrons. Meaning that the mass number of this atom is 12.
To calculate the atomic mass of an element, add up the mass of protons and nuetrons.
When neutrons do not add to the charge of an atom, the number of protons remains the same, so the atomic number stays constant. However, the mass number of the atom increases because neutrons contribute to the mass of an atom without affecting its charge.
no, you add the protons and neutrons