HW1 ENME382 S10 Section0201 solution

HW1 ENME382 S10 Section0201 solution - ENME 382 Section0201...

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1 ENME 382 Section0201 Homework 1 Solution Note: You should get in the habit of showing your work even if you can solve a problem in your head. Reasoning is important and you need to show work to show your reasoning process. 1. Predict the type of bonding that holds the atoms/molecules together in the following solid materials. Explain why you have made the prediction for each material. Where appropriate include calculations. The Sargent-Welsh % ionic character table was used to calculate the % ionicity instead of the formula from the book. You will get similar values using equation in the book . It is important to calculate percent ionicity not just EN. CaO: We need to do a % ionic character calculation for CaO. ( EN=2.5 so %ionic bonding is ~ 79% from S-W table and equation 2.2). Thus, the bonding in CaO is highly ionic and we need to use ionic radii in any calculations. CdS: We need to do a % ionic character calculation for CdS. ( EN=2.5 -1.7= 0.8, so %ionic bonding ~ 15% ). Thus, we would expect covalent bonding to be dominant and we need to use covalent radii (if you are using the table in the front of your text use the atomic radius) for any calculations. FeO: We need to do a % ionic character calculation for FeO. ( EN=1.7 so %ionic bonding ~ 51%). Thus, we would expect ionic bonding to be dominant and we need to use ionic radii. However, it is covalent enough that we need to consider electronic as well as ionic conductivity if we are interested in electrical behavior. Bronze (a copper rich copper-tin alloy): Cu and Sn are both metals so we would expect the bonding to be metallic. Solid Ne : Ne is an inert gas so it already has a stable electron configuration. Thus the bonding in solid Kr is van der Waals bonding. This is why its melting point is -248.7°C or 24.3K. Polyisoprene (a type of rubber): For rubber, the bonding is covalent with some van der Waals. (Rubber is composed primarily of carbon and hydrogen atoms.) – More later in chapter 4. AlP: The positions of Al and P in the periodic table indicate we should do a % ionic character calculation ( EN=0.6 so %ionic bonding ~ 10%). Thus, the bonding is predominantly covalent although it has a small amount of ionic character. You would use covalent radii for this material. Note:
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HW1 ENME382 S10 Section0201 solution - ENME 382 Section0201...

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