Homework 1 Solution

# Homework 1 Solution - MEEN 222-502 Fall 2008 Homework#1...

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MEEN 222-502 Fall 2008 Homework #1 Solution 1. Callister 2.7 The electron configurations for the ions are determined using Table 2.2 (and Figure 2.6). P 5+ : 1s 2 2s 2 2p 6 P 3- : 1s 2 2s 2 2p 6 3s 2 3p 6 Sn 4+ : 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 Se 2- : 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 I - : 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 5s 2 5p 6 Ni 2+ : 1s 2 2s 2 2p 6 3s 2 3p 6 3d 8 2. Callister 2.9 Each of the elements in Group IIA has two s electrons. 3. A copper penny has a mass of 2.60 grams. (a) Give the electronic configuration of copper and indicate which electrons participate in bonding, (b) Calculate the number of copper atoms in the penny (assume that the penny is composed entirely of pure copper). (a) Cu (29) : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 , 3d 10 , 4s 1 electron participates in metallic bonding of copper. (b) 1 amu/atom = 1g/mol, we have 63.54g/mol for Cu. One mole has 6.023*10^23 atoms. 2.60g of Cu is 2.60/63.54 moles * 6.023*10^23 atoms. 4. State the Pauli Exclusion Principle. The Pauli exclusion principle states that each electron state can hold no more than two electrons, which must have opposite spins. No two electrons in an atom share exactly the same quantum numbers. 5. Callister 2.13 The attractive force between two ions F A is just the derivative with respect to the interatomic separation of the attractive energy expression, Equation 2.8, which is just 2 r A dr r A d dr dE F A A = = = The constant A in this expression is defined in footnote 3. Since the valences of the Ca 2+ and O 2- ions (Z 1 and Z 2 ) are both 2, then

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MEEN 222-502 Fall 2008 ( )( ) ( )( ) ( ) ( )( ) ( )( ) N 10 89 . 5 m 10 25 . 1 F/m 10 85 . 8 4 C 10 6 . 1 2 2 4 10 2 9 12 2 19 2 0 2 1 × = × × × = = π πε r e Z e Z F A 6. Describe briefly the 3 types of strong bonds that can form between atoms in a solid. What do melting temperatures tell us about bond strength? Ionic bonding, Covalent bonding, Metallic Bonding Large bonding energy typically indicates high mechanical strength, high melting point and lots of electrons involved in atomic bonding. Therefore, higher melting temperatures of solid materials mean higher bonding strength.
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