Valence outer-shell electrons

Near UY/visible 4-7.5 x 10 7 Valence (outer) shell electrons... 

Figure 1.2.6. The number of valence (outer-shell) electrons for hydrogen and oxygen can be determined from their position in the periodic table. Hydrogen has an atomic number of 1, so it has one proton and one valence electron. Oxygen has a total of eight electrons, but two of these are in a filled shell. Only the outer six electrons are found in the valence shell.

Calculate N, the number of valence (outer) shell electrons needed by all atoms in the molecule or ion to achieve noble gas configurations. Examples ... 

Suppose that you were asked to give the Lewis formula of formic acid, H2CO2, vdiere the atomic number of H is 1, that of C is 6, and that of O is 8. What is the total number of valence (outer shell) electrons that would have to be placed correctly in the structure A, 6 B. 18 C. 20 D, 7 E, 16 ... 

An oxygen atom, which has a strong appetite for electrons, accepts 2 valence (outer shell) electrons from a calcium atom to form a calcium ion, Ca, and an oxide ion, CF+ (Figure 8.2). The loss of electrons by the calcium atom is called oxidation, and the calcium is said to have been oxidized. These terms are derived from the... 

An ojg gen atom, which has a strong appetite for electrons, accepts 2 valence (outer shell) electrons from a calcium atom. 

Lewis developed a special set of symbols for his theory. A Lewis symbol consists of a chemical symbol to represent the nucleus and core (inner-shell) electrons of an atom, together with dots placed around the symbol to represent the valence (outer-shell) electrons. Thus, the Lewis symbol for silicon, which has the electron configuration [Ne]3s 3p, is... 

Visible Excitation of valence and outer-shell electrons UV-visible spectroscopy... 

In forming ions, the transition metals lose their valence (outermost) shell electrons first, followed by their outer d electrons. Note In order for transition metal ions to be colored, the d orbitals must be partially filled. In this case, the solution containing the Ni2+ ion would be colored (green). 

The Lewis electron-dot symbol is a way of representing the element and its valence electrons. The chemical symbol is written, which represents the atom s nucleus and all inner-shell electrons. The valence, or outer-shell, electrons are represented as dots surrounding the atom s symbol. Take the valence electrons, distribute them as dots one at a time around the four sides of the symbol and then pair them up until all the valence electrons are distributed Figure 11.1 shows the Lewis symbol for several different elements. 

Ionised Valency.—This is exemplified by sodium chloride, the sodium atom functioning as a donor by giving its single-valency electron to the chlorine atom, thereby increasing the number of the outer-shell electrons of this latter atom to eight. 

The total number of valence electrons in the molecule (or ion or free radical) must be the sum of all outer-shell electrons contributed to the molecule by each atom plus the... 

Phosphorus is directly below nitrogen in the periodic table. (The relationship of the chemistry of phosphorus to that of nitrogen is somewhat like the sulfur-oxygen relationship discussed in the introduction to Chapter 17.) The phosphorus atom electron configuration is Ne 3.s,23/J3, and it has five outer-shell electrons, as shown by its Lewis symbol in Figure 18.1. Because of the availability of underlying 3d orbitals, the valence shell of phosphorus can be expanded to more than eight electrons. 

Before looking at molecules, we need to review the structure of atoms. Most of the mass of an atom is concentrated in the nucleus. The nucleus consists of protons, which are positively charged, and neutrons, which are neutral. To counterbalance the charge on the nucleus due to the positive protons, the atom has an equal number of negative electrons in shells or orbitals around the nucleus. Because the electrons in the outermost electron shell (the valence electrons) control how the atom bonds, atoms are often represented by their respective atomic symbol surrounded by dots representing the outer-shell electrons. Such representations for some of the elements of interest to us are shown in Figure 1.1. The number of electrons in the valence shell of an atom is the same as the group number of that atom in the periodic table. 

Group Number Valence Electrons Outer Shell Electron Configuration Lewis Structure (Period 2) All Periods are the Same ... 

Determine the number of valence, or outer-shell electrons for each atom in the molecule. For chloroform, we know that carbon has four valence electrons, hydrogen has one valence electron, and each chlorine has seven valence electrons. 

In summary, when metal and nonmetal atoms combine, their valence electrons, which may include all outer-shell electrons of both kinds of atoms, become shared in accordance with their initial electronegativities and in such a way as to provide maximum utilization of orbitals. Through equali-... 

The concept of hybridization described in the previous four sections is not restricted to carbon compounds. Covalent bonds formed by other elements in the periodic table also can be described using hybrid orbitals. Look at the nitrogen atom in ammonia, NH3, for example. A nitrogen atom has five outer-shell electrons and therefore forms three covalent bonds to complete its valence electron octet. 

Chemical bonding usually involves only the outermost electrons of atoms, also called valence electrons. In Lewis dot representations, only the electrons in the outermost occupied r and p orbitals are shown as dots. Paired and unpaired electrons are also indicated. Table 7-1 shows Lewis dot formulas for the representative elements. All elements in a given group have the same outer-shell electron configuration. It is somewhat arbitrary on which side of the atom symbol we write the electron dots. We do, however, represent an electron pair as a pair of dots and an unpaired electron as a single dot. 

Calculate A, the number of electrons available in the valence (outer) shells of all the atoms. For negatively charged ions, add to this total the number of electrons equal to the charge on the anion for positively charged ions, subtract the number of electrons equal to the charge on the cation. Examples ... 

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