Electron-dot formula

Electron-dot formulas can be used to diagram the sharing of valence electrons in molecules and polyatomic ions. The presence of multiple bonds can be identified, and possible resonance structures can be drawn. From the electron-dot formulas, we can predict the three-dimensional shapes and polarities of molecules. Then we examine how the different attractive forces between the particles of ions and molecules influence their physical properties, such as melting and boiling point. Finally, we discuss the physical states of solids, liquids, and gases and describe the energy involved in changes of state. 

Electron-dot formulas for molecular compounds or polyatomic ions use the electron-dot symbols as shown in Table 10.1. For elements with one to four valence electrons, the dots are placed one at a time on the sides, top, and bottom of the atomic symbol. For elements with more than four valence electrons, each added dot is paired with one of the first four dots. 

Draw the electron-dot formulas for molecular compounds or polyatomic ions with multiple bonds and show resonance structures. 

TABLE 10.1 Valence Electrons of Some Representative Elements and Their Electron-Dot Symbols 

When we draw an electron-dot formnla for a molecule or polyatomic ion, we show the sequence of atoms, the bonding pairs of electrons shared between atoms, and the nonbonding or lone pairs of electrons. From the formula, we identify the central atom, which is the element that has the fewer atoms. Then, the central atom is bonded to the other atoms, as shown in Concept Check 10.1. 

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The same G N Lewis who gave us electron dot formulas also suggested a way of think mg about acids and bases that is more general than the Brpnsted-Lowry approach Where Brpnsted and Lowry viewed acids and bases as donors and acceptors of protons (positively charged) Lewis took the opposite view and focused on electron pairs (negatively charged) According to Lewis an acid is an electron pair acceptor and a base is an electron pair donor... 

Though OH is reactive, it is a cluster of atoms with sufficient stability to be identified as a molecule. It is present in a number of high temperature flames, for example. Its chemistry might be expected to be like that of fluorine atoms. Compare the electron dot formulas... 

It is now straightforward to predict that nitrogen will form a stable hydrogen compound with formula NH3. Nitrogen is trivalent. A similar compound, NF3, will be formed with fluorine. The electron dot formulas are... 

Draw electron dot formulas for the molecules CHa, CFa, CHF3, CH2F2, CH3F. Which will be extremely reactive ... 

Electron dot formulas are useful for deducing the structures of organic molecules, but it is more convenient to use simpler representations—structural or graphic formulas—in which a line is used to denote a shared pair of electrons. Because each pair of electrons shared between two atoms is equivalent to a total bond order of 1, each shared pair can be represented by a line between the symbols of the elements. Unshared electrons on the atoms are usually not shown in this kind of representation. The resulting representations of molecules are called graphic formulas or structural formulas. The structural formulas for the compounds (a) to (e) described in Example 21.1 may be written as follows ... 

Lewis structure chem A structural formula in which electrons are represented by dots two dots between atoms represent a covalent bond. Also known as electron-dot formula Lewis formula. Iti-is. strok-char)... 

Le Chatelier s Principle principle that says when a system is at equilibrium and a change is imposed on the system that the system will shift to reduce the change Lewis Electron Dot Formula a diagram showing how the valence electrons are distributed around an atom or distributed in a molecule... 

The first thing you must be able to do in order to predict molecular shapes is to draw an electron-dot formula, so we ll tackle that subject first Including H, there are 16 active nonmetals for which you should know the numbers of valence electrons in the uncombined atoms Except for H (which has only one s electron), these elements are all found to the right of the diagonal in the p block of the periodic table (see inside front cover) Each atom has two v electrons in its valence shell, the number ofp electrons is different for different atoms (Basically, we are uninterested in metals here, metals rarely form predominantly covalent bonds, but tend to form ionic bonds ignore the noble gases, with an already filled s-yi6 unreactive )... 

If you were asked to draw the electron-dot formula for CHUO y0u might be tempted to draw the structure shown in Figure 9-18(a). which would have the A-coplanar structure shown in Figure 9-18(b). This is an ///correct structure... 

A surprising thing is noted when we examine interatomic distances for certain ions and molecules, such as C ()j. no , or ( t H(i. if we draw the usual electron-dot formulas for these, we get the structures shown in Figure 9-20. 

When the unhybridizedp atomic orbitals that are associated with sp- and ip molecular orbitals contain no electrons, we need not worry about them. But every time you draw an electron-dot formula that involves a double or a triple... 

TABLE 4.1. Electron Dot Formulas for Some Representative Elements... 

Formal Charge. Electronic dot formulas essentially convey our notions of how electrons are paired up in molecules. Taking the simplest view, i.e., that an electron-pair bond implies equal sharing of the electron pair between the bonded atoms, one can place a second interpretation on these formulas. This... 

The most apparent similarity within each group is in the electronic dot formulas for the molecules. Insofar as the formulas represent a picture of electron distribution a bonding electron pair is concentrated most strongly in the direction... 

Resonance is the description of the electronic structure of molecules by means of several schemes of pairing electrons (dot formulas), with features of each scheme contributing to the final description. The individual pairing models are called resonance structures. The resonance structures are but partial concepts of the molecules and have physical meaning only in combination with all the other pertinent resonance structures. For nitrate ion we could then write ... 

Relative Importance of Contributing Structures. It is not necessary for alternative electron dot formulas (pairing schemes) to be equivalent for consideration in the over-all combination. For example, one might consider a formula for N03" where there are no multiple bonds. 

Given a periodic table, determine the number of valence electrons of an element and write its electron-dot formula. 

Given a simple molecular formula, draw the electron-dot formula and determine whether each atom in the structure carries a formal charge. 

Draw the electron-dot formulas that show all important contributors to a resonance hybrid and show their electronic relationship using curved arrows. 

In the water molecule, the central atom is O, and the Lewis electron dot formula predicts that there will be two pairs of nonbonding electrons. The oxygen atom will therefore be tetrahedrally coordinated, even though the number of atoms bound to it is only two. The two nonbonding orbitals are very much like the bonding ones, except that there are no other atoms at their far ends. 

The electron-dot formulas for the elements of the second long period are just the same as for the corresponding elements of the first long period ... 

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