Sodium nucleus

As was discussed in Chapter 5 and is indicated in Figure 6.6, the attraction an atom s nucleus has for its valence electrons is weakest for elements on the left in the periodic table and strongest for elements on the right. From sodiums position in the table, we see that a sodium atoms single valence electron is not held very strongly, which explains why it is so easily lost. The attraction the sodium nucleus has for its second-shell electrons, however, is much stronger, which is why the sodium atom rarely loses more than one electron. 

The valence electron of a sodium atom does not sense the full +11 of the sodium nucleus. Why not ... 

Sodium naphthalenide behaves similarly when the solvent is changed from tetrahydrofuran to 1,2-dimethoxyethane. The formation of solvent-separated from contact ion pairs is shown by a dramatic simplification of the ESR spectrum the 100-line spectrum of the contact ion pair, due to the spin-spin coupling of the unpaired electron with the four equal hydrogen nuclei in the a- and y9-positions, together with the sodium nucleus (/ = 3/2), collapses to a 25-line spectrum as the interaction with the sodium ion is disrupted [169, 170]. 

This is one of several reactions of this type in which an organic negative radical-ion and its parent molecule react in the presence of an alkali metal. It is found, rather interestingly, that the rate coefficients depend on the nature of the metal. To account for this, it has been postulated that the metal is involved in a bridging role in the activated complex, e.g., dipy.. K" ". . dipy for the case of 2,2 -dipy-ridyl (dipy) A more extreme case of this association between the radical-ion and the ion of the alkali metal used to form it occurs in the reaction of benzophenone with its negative ion. The spectrum of (benzophenone)" in dme has many hyper-fine lines caused by the interaction of the free electron with the and, when the metal is sodium, the Na nuclei. When benzophenone is added, the structure, due to the proton interaction, disappears and only the lines associated with the sodium interaction remain. To account for this, it has been suggested that the odd electron moves rapidly over all the proton positions too fast for the lines characteristic of the electron in the different proton environments to be seen), but relatively slowly from one sodium nucleus to another. Seen another way, this means that the transfer of an electron from molecule to molecule is associated with the transfer of the cation . ... 

X lO A / m, where A is the mass number of the atomic species. What is the uncertainty in the velocity of a proton trapped within a sodium nucleus with a mass number of 23 ... 

Another form of p decay includes positron emission, where the nucleus expels positively charged positrons. For example, positron emission from a sodium nucleus looks like this ... 

The sodium nucleus has a spin of 1-3/2 and consequently Its relaxation Is dominated by the quadrupolar Interaction of the nuclear quadrupole noment and electric field gradients. The energy lewsle of a spin 3/2 in a magnetic field with quadrupole Interectlon (first order perturhatlon) Is shown In figure 1. 

Now consider the nucleus of some atom, say of the naturally occurring sodium atom. The nucleus contains 11 protons and 12 neutrons. Thus, the charge on the sodium nucleus is -I- lie, which we usually write as simply +11, meaning +11 units of electron charge e. Similarly, the nucleus of a naturally occurring aluminum atom contains 13 protons and 14 neutrons the charge on the nucleus is +13. 

The first ionization energy of sodium is 496 kJ/mol. Use Coulomb s law to estimate the average distance between the sodium nucleus and the 3 electron. How does this distance compare to the atomic radius of sodium Explain the difference. 

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