NE 125 – Winter 2008 Assignment One: Atomic Structure and Bonding Due: 14 January, 2008 1. (From Mid-term exam 2007) In a metal oxide semiconductor device, a thin layer of SiO 2 is grown on a single crystal chip of silicon. How many oxygen atoms are present in an area of 500 μ m x 500 μ m of the oxide layer? Assume the thickness of the layer is 10 nm. 2. The normal boiling point (T nb ) of HF is 19.4°C and the T nb of HCl is -85°C. Explain why hydrogen fluoride (HF) has a much higher boiling point than hydrogen chloride (HCl). Is the bond between H and Cl atoms in molecules of HCl an ionic bond? Calculate and compare the percentage ionic character of the interatomic bond of HF to MgO. 3. (Ionic Bonding) Magnesia (MgO) is a hygroscopic white ionic solid. Crystalline MgO is used in infrared optics and other optical applications. Due to its refractory nature, MgO is also used as a liner for crucibles and as a material of construction for fireproofing. It is also used extensively as an insulating material. (a)
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