Re: Questions about Size of Atoms?

Followings can be relevant snips:-

""why do electrons move, where do they gain the energy for this
movement, as they never stop moving within their energy levels does it
mean their energy is infinite?


Electrons move all the time. There are two kinds of "perpetual motion
machines" -- machines in which the parts move all the time, and
machines from which you can extract energy from it while leaving it in
the original state. The first kind doesn't violate energy conservation
or anything -- motion may continue indefinitely without adding or
subtracting energy -- there's no "friction" for electrons in their
lowest energy state orbits around atomic nuclei. There's also no
average velocity of these electrons either, but if you were to make a
measurement of the instantaneous speed of an electron in an atom at any
instant of time, you will find it is moving.

What makes this all okay is that the electrons cannot lose energy if
they are already in their lowest energy state. Quantum mechanics has
the weird feature that there is such a thing as a lowest energy state,
which is usually a tightly bound state where the electron is found
close to the nucleus of an atom. Get it any closer on average, and you
have to confine it to a smaller volume of space. Confining electrons to
small volumes of space incereases the expectation value of their speed
(while reducing the electrostatic potential energy because opposite
charges attract). At some happy equilibrium, the energy is minimized --
bring the electron in closer and it has to move more quickly,
increasing energy, take it away, and the electrostatic potential energy
is higher. ""

""According to kinetic theory, there should be no movement of
individual molecules at absolute zero, so any material at this
temperature would be solid. In a monatomic gas, most of the energy is
in the form of translational motion, and the temperature can be
measured in terms of the distribution of this motion, with slower
speeds corresponding to lower temperatures, perhaps even down to
absolute zero. But this is contrary to experimental evidence, and it is
predicted that helium will never solidify, no matter how much it is
cooled or compressed.

Because of quantum-mechanical effects, the speed at absolute zero is
larger than zero and depends, along with the energy, on the volume
within which a particle is confined. At absolute zero, the molecules
and atoms in a system are all in their ground state, the state of
lowest possible energy, and a system has the least amount of kinetic
energy allowed by the laws of physics. But the lowest possible
zero-point energy for a confined particle in a box is not zero. Rather
than being fixed and non-moving, the equation for the energy levels
shows that no matter how low the temperature gets, even when the
quantum number takes its minimum value of one, a particle still has
some translational kinetic energy and motion. This is a reflection of
Heisenberg's uncertainty principle, which states that the position and
the momentum of a particle cannot both be known precisely at any given
time. http://en.wikipedia.org/wiki/Absolute_zero ""

""According to the third law of thermodynamics, a system at absolute
zero temperature exists in its ground state; thus, its entropy is
determined by the degeneracy of the ground state. Many systems, such as
a perfect crystal lattice, have a unique ground state and therefore
have zero entropy at absolute zero (because ln(1) = 0).
In physics, the ground state of a quantum mechanical system is its
lowest-energy state. An excited state is any state with energy greater
than the ground state(that is, more energy than the absolute minimum).
http://en.wikipedia.org/wiki/Ground_state ""

It looks that at "absolute zero" without external
influences(interventions), electrons have no or least motion and they
are at ground state. They come into excited states on external
influences, increase in temp. ot other influences/interventions and
also gain motion. Such motion of electron may also influence motion or
location of protons due to balancing in atrractive forces in between
them(about neutrons, I can't say). This may also increase the size of
atoms as electrons gain more negative charge . The excess negative
charge results in a lowered attraction between nuclei and electrons so
atom size increased of anions compared to the neutral atoms.

We may need to understand what decide motion of electrons, charge &
size of atoms--whether external influences or attractive forces between
nucleus/protons and electrons??

.

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