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Unit 9 CHEMICAL BONDING

Photochemical smog contains N02, the gas responsible for the brown blanket over larger cities. This gas can produce a dimer (two identical units chemically bonded) by the reaction, 2N02 —> N204. If the reaction of 750 g N02 goes all the way to the right, what will be the pressure in a 10-L chamber at 42°C ... [Pg.90]

When two elements form an ionic compound, is an electron really lost by one atom and transferred to the other one In order to deal with this question, consider the data on the ionic solid LiF. The average radius of the neutral Li atom is about 2.52k. Now if this Li atom reacts with an atom of F to form LiF, what is the average distance between the Li nucleus and the electron it has lost to the fluorine atom The answer is 1.56A the electron is now closer to the lithium nucleus than it was in neutral lithium. So the answer to the above question is both yes and no yes, the electron that was now in the 2s orbital of Li is now within the grasp of a fluorine 2p orbital, but no, the electron is now even closer to the Li nucleus than before, so how can it be lost The one thing that is inarguably true about LiF is that there are more electrons closer to positive nuclei than there are in the separated Li and F atoms. But this is just the rule we stated at the beginning of this unit chemical bonds form when electrons can be simultaneously near two or more nuclei. [Pg.27]

Likewise, a basis set can be improved by uncontracting some of the outer basis function primitives (individual GTO orbitals). This will always lower the total energy slightly. It will improve the accuracy of chemical predictions if the primitives being uncontracted are those describing the wave function in the middle of a chemical bond. The distance from the nucleus at which a basis function has the most significant effect on the wave function is the distance at which there is a peak in the radial distribution function for that GTO primitive. The formula for a normalized radial GTO primitive in atomic units is... [Pg.234]

Fig. 1). A polymer chain is made of effective monomers joined by bonds. A bond corresponds to the end-to-end distance of a group of 3-5 successive chemical bonds and can fluctuate in some range. It is represented by vectors 1 of the set P(2,0,0),P(2,1,0),P(2,1,1),P(3,0,0), and P(3,l,0) which guarantee that intersections of the polymer chain with other chains, or with itself, are virtually impossible. All lengths are here measured in units... Fig. 1). A polymer chain is made of effective monomers joined by bonds. A bond corresponds to the end-to-end distance of a group of 3-5 successive chemical bonds and can fluctuate in some range. It is represented by vectors 1 of the set P(2,0,0),P(2,1,0),P(2,1,1),P(3,0,0), and P(3,l,0) which guarantee that intersections of the polymer chain with other chains, or with itself, are virtually impossible. All lengths are here measured in units...
Total energies are always negative numbers and, in comparison with the energies of chemical bonds, are very large. They are generally expressed in so-called atomic units or au, but may be converted to other units as desired ... [Pg.13]

At present it is believed that intermolecular chemical bonds are formed during the vulcanization of polychloroprene with ZnO not only due to the mobile chlorine in allyl position but also as a result of the reaction of the chlorine located directly at the double bond of the monomeric units chloroprene connected in the chain in 1,4-position as shown in the following scheme43. ... [Pg.112]

The nitrate anion is a group of four atoms held together by chemical bonds. The entire unit bears a -1 electrical charge. [Pg.139]

Electronegativities, which have no units, are estimated by using combinations of atomic and molecular properties. The American chemist Linus Pauling developed one commonly used set of electronegativities. The periodic table shown in Eigure 9 7 presents these values. Modem X-ray techniques can measure the electron density distributions of chemical bonds. The distributions obtained in this way agree with those predicted from estimated electronegativities. [Pg.579]

For the most part, plastics are man-made since very few plcistlcs are natural, i.e.- nature-made. Natural plastics include large molecular-wei t proteins and similar molecules. Man-made plastics can be classified as either thermoplastic or thermosetting. Each class derives its physical properties from the effects of application of heat, the former becoming "plastic" (that is- it becomes soft and tends to flow) while the latter becomes less "plastic" and tends to remain in a softened state. This difference in change of state derives from the actual nature of the chemical bonds in the polymer. Thermoplastic polymers generally consist of molecules composed of many monomeric units. A good example is that of polyethylene where the monomeric unit is -(CH2-CH2)-. The molecule is linear... [Pg.403]

As the result of theoretical consideration of polycondensation of an arbitrary mixture of such monomers it was proved [55,56] that the alternation of monomeric units along polymer molecules obey the Markovian statistics. If all initial monomers are symmetric, i.e. they resemble AaScrAa, units Sa(a=l,...,m) will correspond to the transient states of the Markov chain. The probability vap of transition from state Sa to is the ratio Q /v of two quantities Qa/9 and va which represent, respectively, the number of dyads (SaSp) and monads (Sa) per one monomeric unit. Clearly, Qa(S is merely a ratio of the concentration of chemical bonds of the u/i-ih type, formed as a result of the reaction between group Aa and Ap, to the overall concentration of monomeric units. The probability va0 of a transition from the transient state Sa to an absorbing state S0 equals l-pa where pa represents the conversion of groups Aa. [Pg.188]

A chemical equation describes a chemical reaction in many ways as an empirical formula describes a chemical compound. The equation describes not only which substances react, but the relative number of moles of each undergoing reaction and the relative number of moles of each product formed. Note especially that it is the mole ratios in which the substances react, not how much is present, that the equation describes. In order to show the quantitative relationships, the equation must be balanced. That is, it must have the same number of atoms of each element used up and produced (except for special equations that describe nuclear reactions). The law of conservation of mass is thus obeyed, and also the "law of conservation of atoms. Coefficients are used before the formulas for elements and compounds to tell how many formula units of that substance are involved in the reaction. A coefficient does not imply any chemical bonding between units of the substance it is placed before. The number of atoms involved in each formula unit is multiplied by the coefficient to get the total number of atoms of each element involved. Later, when equations with individual ions are written (Chap. 9), the net charge on each side of the equation, as well as the numbers of atoms of each element, must be the same to have a balanced equation. The absence of a coefficient in a balanced equation implies a coefficient of 1. [Pg.114]


See other pages where Unit 9 CHEMICAL BONDING is mentioned: [Pg.203]    [Pg.230]    [Pg.3]    [Pg.4796]    [Pg.86]    [Pg.155]    [Pg.226]    [Pg.252]    [Pg.118]    [Pg.1496]    [Pg.428]    [Pg.159]    [Pg.276]    [Pg.563]    [Pg.157]    [Pg.497]    [Pg.1135]    [Pg.15]    [Pg.39]    [Pg.463]    [Pg.867]    [Pg.165]    [Pg.530]    [Pg.379]    [Pg.600]    [Pg.354]    [Pg.196]    [Pg.696]    [Pg.190]    [Pg.196]    [Pg.196]    [Pg.197]    [Pg.27]    [Pg.457]    [Pg.485]    [Pg.106]    [Pg.15]    [Pg.29]    [Pg.367]    [Pg.6]   


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