Hi again, answer123,
The answer is e) binding energy.
According to my physics book:
"... for each kind of atom, the atomic mass is always less than the
sum of the masses of the constituent particles in their free states".
"The New Physics" by Douglas Paul, et al. Holt, Rinehart and Winston
of Canada, Ltd (1977)
This "loss" in mass is attributed to binding energy. It happens
because nucleons (elementary particles, like neutrons and protons) in
their free states are at a higher energy state than when they are part
of an atom. To be a free particle means that the nucleon must have
enough kinetic energy to have broken free from an atom.
As nucleons combine to form an atom, energy is given off because the
chemical system is now in a more stable state. The original kinetic
energy that the nucleons had is given up and released into the
surroundings. The energy that is given off is called binding energy.
Binding energy is related to mass because of Einstein's famous E=mc^2
equation. A little mass can be converted into lots of energy and vice
versa. As the nucleons combine to form the atom, the binding energy
that is lost comes in the form of a reduction in mass.
Thus, in the example:
Two free protons and two free neutrons have kinetic energies that
prevent them from clumping together to form an atom. But when they do
form an atom, that kinetic energy is given off as the helium-4 atom
comes together. This energy is binding energy, and the energy is lost
by a reduction of mass of the particles. For this reason, the mass of
He-4 is less than that of 2 protons and 2 neutrons.
Reference
"The New Physics" by Douglas Paul, et al. Holt, Rinehart and Winston
of Canada, Ltd (1977) |
