ull mobily 3:27 PM 79% bbappsrv.pmu.edu.sa c Materials Engineering (MEEN 2211) Instructor: Dr. Ragu Kannan Spring 2018 Homework 1 Deadline: Sunday, 25 Feb 2018 1st Homework 2.1 Cite the difference between atomic mass and atomic weight. 2.2 Chromium has four naturally occurring isotopes: 4.34% of "Cr, with an atomic weight of 49.9460 amu, 83.79% of Cr, with an atomic weight of 51.9405 amu, 9.50% of Cr, with an atomic weight of 52.9407 amu, and 2.37% of Cr, with an atomic weight of 53.9389 amu. On the basis of these data, confirm that the average atomic weight of Cr is 51.9963 amu. 2.3 (a) How many grams are there in one amu of a material? (b) Mole, in the context of this book, is taken in units of gram-mole. On this basis, how many atoms are there in a gram-mole of a substance? 2.11 Without consulting Figure 2.8 or Table 2.2, determine whether each of the electron configurations given below is an inert gas, a halogen, an alkali metal, an alkaline carth metal, or a transition metal. Justify your choices. (a) 1s 2s 2p 3s 3p 3d 4s (b) 1s 2s 2p 3s 3p (c) 1s 2s 2p (d) 1s 2s 2p 3s (e) 1s 2s22p"3s23p"38-4s (f) 1.s22s22p 3s 3p4s! 2.13 Calculate the force of attraction between a Kt and an O2-ion the centers of which are separated by a distance of 1.6 nm. 2.18 (a) Briefly cite the main differences between ionic, covalent, and metallic bonding. (b) State the Pauli exclusion principle. 2.21 Explain why hydrogen fluoride (HF) has a higher boiling temperature than hydrogen chloride (HCI) (19.4 vs. --85°C), even though HF has a lower molecular weight. <
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