What is a net

Depending on your previous experience, this question may seem a bit odd You solve your crystal structure, you see molecules acting as connection points, and you see other molecules acting as rods connecting these nodes. If the resulting geometric pattern extends infinitely in the and z- directions, then you have a 3D-net. What more is there to say  

In the words of Gautam Desiraju First we did not draw any lines, then we got close packing. Then we started to draw lines and got molecules. We drew more lines and got networks. If we continue to draw more and more lines, then we get back to close packing again [2] 

In this Chapter, we will not tell you when you can or cannot draw bonds or dotted lines. Rather, we will try to discuss when it is meaningful to describe a structure in terms of a net and let you come to your own conclusions. 

Finding out if this is the case is often easier said than done. However, we suggest some general guidelines  

It has been suggested that every figure containing dotted lines should be accompanied by the appropriate definition used when drawing this line. 

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What is a net ionic equation How does it differ from a complete ionic equation (10.3)... 

What is a net ionic equation What is the value in using a net ionic equation Give an example. 

Example 5 Radiation in a Furnace Chamber A furnace chamber of rectangular paraUelepipedal form is heated hy the combustion of gas inside vertical radiant tubes hningthe sidewalls. The tubes are of 0.127-m (5-in) outside diameter on 0.305-m (12-in) centers. The stock forms a continuous plane on the hearth. Roof and end walls are refractory. Dimensions are shown in Fig. 5-20. The radiant tubes and stock are gray bodies having emissivities of 0.8 and 0.9 respectively. What is the net rate of heat transmission to the stock by radiation when the mean temperature of the tube surface is SIG C (1500 F) and that of the stock is 649 C (1200 F) ... 

A plate. 1 m in diameter at 750 K, is to be heated by placing it beneath a hemispherical dome of the same diameter at 1200 K the distance between the plate and the bottom of the dome being 0.5 m, as shown in Figure 9.42. If the surroundings are maintained at 290 K, the surfaces may be regarded as black bodies and heat transfer from the underside of the plate is negligible, what is the net rate of heat transfer by radiation to the plate ... 

There are a host of physical questions that cannot be easily answered just by knowing the rates listed in Fig. 6.13. For example, once an Ag atom is deposited on the surface, how long will it be (on average) before that Ag atom visits a site adjacent to a Pd surface atom How many different Pd surface sites will an Ag atom visit per unit time on the surface What is the net diffusion coefficient of Ag atoms on this surface To answer these questions, we need a tool to describe the evolution in time of a set of Ag atoms on the surface. 

In a normal resting subject who is receiving no drugs, there is a moderate parasympathetic tone to the heart, and sympathetic activity is relatively low. The ventricular muscle receives little, if any, parasympathetic innervation. As the blood pressure rises in response to norepinephrine, the baroreceptor reflex is activated, parasympathetic impulses (which are inhibitory) to the heart increase in frequency, and what little sympathetic outflow there is may be reduced. Heart rate is slowed so much that the direct effect of norepinephrine to increase the rate is masked and there is a net decrease in rate. Under the conditions described, however, the impact of the reflex on the ventricles is very slight because there is no parasympathetic innervation and the preexisting level of sympathetic activity is already low. A further decrease in sympathetic activity therefore would have little further effect on contractility in this subject. Thus, a decrease in heart rate and an increase in stroke volume will occur, and cardiac output will change very little. 

What is the net thermochemistry in a reaction such as 11.2 or 11.4 In the atomic site convention, the bookkeeping is quite straightforward. In reaction 11.2 we have converted AsH3(g) and Ga(s) into AsH3(s) and Ga(b). Thus the change in a thermochemical property (e.g., AHr) is just the difference in the heats of formation of the products and the reactants. What about in the open site convention What are the properties of 0(s), the open site Because these two formalisms describe an identical physical event, it is evident the properties of the open site must be related to those of Ga(b) and Ga(s). For example, the heat of formation of this open site is just... 

Solve the HMO equations for the a orbitals and orbital energies of the C—C and C—O bonds assume that h(O) = h(C) — hco >hcc = hCo, and Sco = 0. Sketch the results in the form of an interaction diagram. Which bond is stronger Calculate the homolytic bond dissociation energies in units of hcc - What is the net charge on O, assuming that it arises solely from the polarization of the a bond ... 

What is the net sample rate and its uncertainty This raises the general question of calculating the uncertainty in the result of some mathematical operations on an uncertain number. If we consider two independently determined numbers and their uncertainties (standard deviations), A + [Pg.572]

A-8. The cyanate ion contains 16 valence electrons, and its three atoms are arranged in the order OCN. Write the most stable Lewis structure for this species, and assign a formal charge to each atom. What is the net charge of the ion ... 

M8 Two perfectly black parallel planes 1.2 by 1.2 m are separated by a distance of 1.2 m. One plane is maintained at 800 K and the other at 500 K. The planes are located in a large room whose walls are at 300 K. What is the net heat transfer between the planes ... 

No oxygen is consumed, and we move only a little way down the energy hill toward carbon dioxide and water. What is important is that a start has been made in breaking the five carbon-carbon bonds of glucose, and that two molecules of A DP are converted into ATP. (ATP is required for some of the steps of glycolysis, but there is a net production of two molecules of ATP for each molecule of glucose consumed.)... 

Write the electrode reactions for a cell that involves only Cu(5 ) and Cu (a ) in which the anode reaction is the reverse of the cathode reaction. What is the net result of operating this cell ... 

Now, let s examine what happens to heat in this situation. Because engine 1 is more efficient than engine 2 and because the work is the same for both, engine 1 must withdraw less heat from the hot reservoir at Th than is discharged into the same reservoir by engine 2 there is a net transfer of heat into the high-temperature reservoir. For the combined engines, AU = =... 

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