Main-group ions, electron configurations

The formulas and electron configurations of the most common main-group ions are listed in Table 6.1. 

The electronic configurations of transition metal ions, like those of main group ions, are determined by removal of the electrons from the shell of highest n value first. Next, electrons may be lost from the d subshell next to the valence shell. The capability of removing a variable number of electrons makes it possible for most transition metals to have ions of different charges. 

Estimation of the entropy of solvation requires calculation of the entropy of the ion in the gas phase. For a monoatomic ion, the main contribution to the entropy comes from its translational energy. Simple ions formed from the main group elements have the electronic structure of an inert gas and therefore do not have an electronic contribution to the entropy. On the other hand, ions formed from transition metals may have an electronic contribution to the gas phase entropy, which depends on the electronic configuration of the ion s ground state and of any other electronic states which are close in energy to the ground state. The translational entropy is given by the Sackur-Tetrode equation, which is obtained from the solution of the SWE for a particle in a box (see section 2.2)... 

Electron Configurations of Main-Group Ions In Chapter 2, you learned the symbols and charges of many monatomic ions. But why does an ion have a particular charge in its compounds Why is a sodium ion Na and not Na ", and why... 

Figure 8.18 Main-group ions and the noble gas electron configurations.

SAMPLE PROBLEM 8.6 Writing Electron Configurations of Main-Group Ions Problem Using condensed electron configurations, write reactions for the formation of the common ions of the following elements ... 

Electron Configurations of Transition Metal Ions In contrast to most main-group ions, transition metal ions rarely attain a noble gas configuration, and the reason, once again, is that energy costs are too high. The exceptions in Period 4 are scandium, which forms Sc ", and titanium, which occasionally forms Ti in some compounds. The typical behavior of a transition element is io form more than one cation by losing all of its ns and some of its (n — l)d electrons. (We focus here on the Period 4 series, but these points hold for Periods 5 and 6 also.)... 

Electron Configurations of Main-Group Ions Why does an ion have a particular charge Na not Na, or F not P Why do some metals form two ions, such as Sn + and Sn The answer relates to the location of the element in the periodic table and the energy associated with losing or gaining electrons ... 

Writing electron configurations of ions Given an ion, write the electron configuration. For an ion of a main-group element, give the Lewis symbol. (EXAMPLES 9.2,93)... 

To write the electron configuration of an ion formed by a main group element, we first write the configuration for the atom and either add or remove the appropriate number of electrons. Electron configurations for the sodium and chloide ions ate... 

Sample Problem 7.6 gives you some practice writing electron configurations for the ions of main group elements. 

For main-group ions, the order of removing electrons is the same as the order in which they are added in building up the electron configuration. 

Transition metal ions have an incompletely filled d-shell, i.e. their electron configuration is d". The optically active electrons are thus bound to central potential as well as experiencing crystal field potential, and are not shielded by outer electrons. Most transition metal ions are multi-valent. Mainly the number of 3d electrons and the crystal field determine their optical properties. Thus the groups below have similar optical behavior ... 

Main group (s-block and p-block) elements generally form ions with closed shell configurations (e.g. Na+, Mg2+, Al3+) in which all electrons have been lost from the valence shell, an anions (F-, O2-) in which valence shell has been filled. 

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