Sodium effective nuclear charge

Account for the fact that the ionization energy of potassium is less than that of sodium despite the latter having the smaller effective nuclear charge. 

Sodium is in Group 1 of the periodic table and can be expected to form a +1 ion. However, the valence electron is tightly held by the effective nuclear charge—... 

The observed inter-atomic distances (Table XIX) for the beryllium salts are somewhat smaller than those calculated. This indicates that there is more deformation in these crystals than in the sodium chloride type crystals, despite the smaller effective nuclear charge of the two-shell cation and points to the existence of an increased tendency to deformation... 

A Procedure to Obtain the Effective Nuclear Charge from the Atomic Spectrum of Sodium 155... 

Which experiences a greater effective nuclear charge, an electron in the outermost occupied shell of neon or one in the outermost occupied shell of sodium Why ... 

An electron in the outermost shell of sodium experiences the greatest effective nuclear charge because it is closer to the nucleus and electric forces diminish over distance. 

The nuclear charge experienced by an electron in sodium s third shell is not strong enough to hold this many electrons. As was discussed in Chapter 5, this is because there are 10 inner-shell electrons shielding any third-shell electron from the +11 nucleus. The effective nuclear charge in this shell, therefore, is about +1, which means that it is able to hold at most one electron. 

The electron configuration for sodium is l5 2r 2/f 3r. In which of these orbitals do the electrons experience the greatest eflective nuclear charge How about the weakest effective nuclear charge ... 

A FIGURE 7.2 Effective nuclear charge. The effective nuciear charge experienced by the vaience eiectron in a sodium atom depends mostiy on the 11 + charge of the nucieus and the 10- charge of the core eiectrons. 

Let s look at the Na atom to see what to expect for the magnitude of Z ff. Sodium has the electron configuration [Ne]3s. The nuclear charge is Z = 11 +, and there are 10 core electrons (ls 2s 2p ). We therefore expect S to equal 10 and the 3s electron to experience an effective nuclear charge of Z ff = 11 — 10= +( FIGURE 7.2). The situation is more complicated, however, because the 3s electron has a small probability of being doser... 

The first ionization energies of sodium, potassium and rubidium atoms are 5.14, 4.34 and 4.17 eV, respectively. Use equation (7.37) to calculate the effective nuclear charge experienced by the outermost s electron in each of these atoms. 

Elemental cesium reacts more violently with water than does elemental sodium. Which of the following best explains this difference in reactivity (i) Sodium has greater metallic character than does cesium, (ii) The first ionization energy of cesium is less than that of sodium, (iii) The electron affinity of sodium is smaller than that of cesium, (iv) The effective nuclear charge for cesium is less than that of sodium, (v) The atomic radius of cesium is smaller than that of sodium. 

---