Nucleus size analogies

One of the features of the hydrogen atom for which observations need to be reconciled with the quantum mechanical picture is the size of the atom. The quantum mechanical description gives a probability distribution for finding the electron located about the nucleus. In analogy... 

As we move down the family of alkali metals on the periodic table, metal chemical reactivity increases. This increase in reactivity corresponds to an increase in atomic size. As atomic size increases, the outermost electrons are farther from the atomic nucleus. The positively charged protons in the atomic nucleus are trying to attract the negatively charged outermost electrons, but attractive force decreases as distance increases. This is analogous to a mother trying to keep her children home while the children, as they become more energetic, wander farther away and often eventually leave home. A child can leave home more easily when already distanced from home. Therefore, cesium (Cs), in which the outermost electron is far from the positive nucleus and can easily leave home, is much more chemically reactive than lithium (Li), in which the outermost electron is close to home, the nucleus. 

The structure of the atom and the organization of the periodic table are so inextricably intertwined as to be inseparable. We will examine the structure of the atom first and then see how this structure determines the arrangement and function of the periodic table. The twentieth century was the setting for the unraveling of many secrets of the atom, with the remainder of its secrets on the scientific horizon. At the beginning of the century, the atom was viewed as a small, solid unit. Early in that century, Ernest Rutherford s experiments showed it to be mostly empty space—a truly startling idea said to be the shot heard round the scientific world. His work led to the conclusion that the atom has a dense, positive center, called the nucleus that is quite small compared to the entire atom. An analogy can be drawn about this size comparison If the whole atom were the size of Yankee Stadium, the nucleus would be the size of the baseball held by the pitcher. 

The effeet of the nonzero size of the nueleus is small, so it is almost never taken into aeeount in eomputations. If we enlarged the nueleus to the size of an apple, the first Bohr orbit would be 10 km from the nueleus. And still (stieking to this analogy), the electron is able to distinguish a point from an apple Not quite, it sees the (tiny) difference because the electron knows the region close to the nucleus it is there that it resides most often. Anyway, the theory is able to compute such a tiny effect. 

A reasonable way to estimate the size of the correlation correction to the relativistic tp potential is to make use of the semi-relativistic multiple scattering formalism [Ra 85] discussed in section 4.2. In analogy with the Watson theory, the leading correlation correction is quadratic in the relativistic NN invariant scattering operator and is proportional to two-body correlations in the target nucleus. 

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