Classical group numbers

The number of outermost electrons is crucial to the chemical bonding of the atom. (See Chap. 5.) For main group elements, the number of outermost electrons is equal to the classical group number, except that it is 2 for helium and 8 for the other group 0 (18) elements. (It is equal to the modern group number minus 10 except for helium and the first two groups.)... 

FigHre 5.7 Numbers of Valence Electrons for Atoms of Classical group number Modern group number lA 1 IIA 2... 

The charge on every monatomic anion (except H ) is equal to the classical group number of the element minus 8. The number of added electrons is the absolute value of that difference. 

The alkali metals, the alkaline earth metals, the group IIIB metals, aluminum, zinc, cadmium, and silver have ions with charges equal to their classical group numbers, but only in their compounds When the elements are uncombined, they do not form ions, and the charge on each atom is zero. 

All monatomic anions are named by changing the ending of the element s name to -ide. For example, I, H, and are called iodide ion, hydride ion, and oxide ion, respectively. (The names of a few special anions also end in -ide among the most important are hydroxide and cyanide ions, listed in Table 6.4.) The charge on any monatomic anion is constant and, except for that on H , is equal to the classical group number minus 8 (see Figure 5.11). 

The maximum oxidation number for most elements is equal to the classical group number of the element. 

Oxidation number is a periodic property. For example, for most elements the maximum oxidation number is equal to the classical group number, and the minimum oxidation number for nonmetals other than hydrogen is the group number minus 8. 

The metals of parts (a) and (b) have charges equal to their classical group numbers. For parts (c) and (d), each monatomic anion has a charge equal to its classical group number minus 8 (or the modem group number minus 18). 

Ans. Fe (F is a main group element, with valence electrons equal to its classical group number.)... 

Which classical periodic group number is used for each of the following families ... 

The valence shell of electrons in an atom is the outermost shell of electrons of the uncombined atom. The electrons in that shell are called valence electrons. If all the electrons are removed from that shell, the next inner shell becomes the new outermost shell. For example, the sodium atom has 2 electrons in its first shell, 8 electrons in its second shell (the maximum), and its last electron in its third shell. The valence shell is the third shell. If the 1 electron is removed from the third shell, the second shell becomes the outeamost shell, containing 8 electrons. The valence shell is still the (now empty) third shell. The number of electrons in the valence shell of an uncombined main group atom is equal to the classical periodic group number of the element (Figure 5.7). The exceptions to this rule are that hehum has 2 valence electrons and the other noble gases have 8 valence electrons. 

In compounds, the metals of periodic groups iA, iiA and IIIB (1, 2, and 3), as well as zinc, cadmium, aluminum, and silver, always form ions with positive charges equal to the element s classical periodic group number. 

In which classical periodic groups are the atoms valence electrons equal in number to the group number ... 

Naming the constant type of cation involves naming the element and adding the word ion, unless a compound is being named. For example, is the potassium ion, and Ca is the calcium ion KCl is potassium chloride. The alkali metals, the alkaline earth metals, zinc, cadmium, aluminum, and silver are the most important metals that form ions of the constant type (Figure 6.2). Each of these metals forms the same ion in any of its compounds, and the charge on the ion is equal to the classical periodic group number. 

Atoms of the main group elements except for the noble gases have valence electrons equal in number to their (classical) periodic group numbers. 

The Group lA, IIA, and IIIB metals, zinc, cadmium, silver, and aluminum form a single type of ion with charge equal to the metal s classical periodic group number. 

The elements that form only one cation are the alkali metals (group lA), the alkaline earth metals (group HA), zinc, cadmium, aluminum, and most often silver. The charge on the ions that these elements form in their compounds is always equal to their classical periodic table group number (or group number minus 10 for Ag, Cd, Zn, and A1 in the modern labeling system in the periodic table). 

Scale-up in fixed bowl mixer-granulators has been studied by Rowe and Cliffs group using the classical dimensionless numbers of Newton (power), Reynolds, and Froude to predict the end-point in geometrically similar high-shear Fielder PMA 25, 100, and 600 L machines. 

Besides the five classical types there are borderline cases which, as in most classifications, are difficult to assign to one group rather than another. There are indeed a not inconsiderable number of isotherms which are difficult to fit into the classification at all. 

Similarity Variables The physical meaning of the term similarity relates to internal similitude, or self-similitude. Thus, similar solutions in boundaiy-layer flow over a horizontal flat plate are those for which the horizontal component of velocity u has the property that two velocity profiles located at different coordinates x differ only by a scale factor. The mathematical interpretation of the term similarity is a transformation of variables carried out so that a reduction in the number of independent variables is achieved. There are essentially two methods for finding similarity variables, separation of variables (not the classical concept) and the use of continuous transformation groups. The basic theoiy is available in Ames (see the references). 

Dukler Theory The preceding expressions for condensation are based on the classical Nusselt theoiy. It is generally known and conceded that the film coefficients for steam and organic vapors calculated by the Nusselt theory are conservatively low. Dukler [Chem. Eng. Prog., 55, 62 (1959)] developed equations for velocity and temperature distribution in thin films on vertical walls based on expressions of Deissler (NACA Tech. Notes 2129, 1950 2138, 1952 3145, 1959) for the eddy viscosity and thermal conductivity near the solid boundaiy. According to the Dukler theoiy, three fixed factors must be known to estabhsh the value of the average film coefficient the terminal Reynolds number, the Prandtl number of the condensed phase, and a dimensionless group defined as follows ... 

---