So, let us first revise how the atom is currently described by modern physics. Electrons are said to be in constant motion around the nucleus, protons and neutrons jiggle within the nucleus, and quarks jiggle within the protons and neutrons. Electrons, protons and neutrons are considered to be 'hard' particles.
This above picture is not to scale. If we drew the atom to scale and made protons and neutrons a centimeter in diameter, then the electrons and quarks would be less than the diameter of a hair and the entire atom's diameter would be greater than the length of thirty football fields! 99.999999999999% of an atom's volume is just empty space! Do you really believe that over 99.99% of the building block of matter is just empty space? If you DO NOT, then you are on the right track. The following is a list describing the currently accepted model of the atom.
1. At the center of the atom is a small, dense positively charged nucleus consisting primarily of protons and neutrons. Protons consist of two up quarks and a down quark (uud). Neutrons consist of two down quarks and an up quark (ddu).
2. Moving around the nucleus are negatively charged electrons which account for only 1/5000 of the atom's mass -- the rest of the mass being in the nucleus. Most of the atom is empty space. The motion of the electrons is not described.
3. The electrons in an atom are allowed to have only certain energies. The allowed states are described by a set of "quantum numbers", which indicate their average distance from the nucleus, their angular momentum and its direction, and the electrons' spin direction.
4. Light of a specific color is emitted or absorbed when electrons change from one state to another.
5. The "Heisenberg Uncertainty Principle" states that the position and momentum of an electron cannot be simultaneously determined. Since Bohr's orbiting electron model failed to describe the actual orbital distribution of the electron cloud, it had been concluded that the electrons motion it not governed by any ordered motion, but is completely random. The interpretation of the Heisenberg principle is that the atom's structure and the interactions of its electrons are random and can be discussed only statistically. The orbitals are therefore just a probabilistic distribution of such a random motion.
6. Even though the electron's exact position cannot be determined, if its energy is known, the theory predicts the probability that an electron could be at a particular place.
7. If the probability location of an electron of known energy is plotted in space, the plot looks like a fuzzy cloud of varying density, the shape varying with differences in angular momentum. It always has a definite symmetry about the nucleus. Some of the clouds or orbitals are spherical, others are like dumbbells, while others are more complex.
8. In describing an atom with many electrons, the charge clouds of one shell are superimposed in space with those of other shells.
