problems_section_2

problems_section_2 - Section 2 Problems Atomic Structure...

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Section 2 Problems – Atomic Structure and Bonding 1. An interconnect is a small wire between two points on a semiconductor device. For a copper interconnect with a rectangular cross section which is 5 μ m wide, 1 μ m thick, a 1 mm long, estimate how many atoms are contained in the interconnect. 2. The density of tungsten (W) wire is 19.3 g/cm 3 . Its atomic weight is 183.85 g/mole. Estimate how many W atoms are contained in a piece of tungsten wire which has a diameter of 1 mm and a length of 1 cm such as might be found in the filament of an incandescent light bulb. 3. Wafers of silicon are used to make semiconductor devices. The density of silicon is 2.33 g/cm 3 and its atomic weight is 28.086 g/mole. Estimate how many Si atoms are contained in a single- crystal wafer 500 μ m thick and 15 cm in diameter. If this wafer is uniformly doped (lightly alloyed) with 10 16 phosphorus atoms per cubic centimeter, what is the atomic fraction of phosphorus in silicon? 4. Aluminum foil used for storing food weighs about 0.3g/in 2 . Estimate how many atoms are contained in one square inch of aluminum foil. Estimate the volume per aluminum atom and, from this, determine a dimension characteristic of a single aluminum atom. Compare your estimate value to the tabulated atomic radius for aluminum. 6. The density of Na is 0.97 g/cm 3 , and its atomic weight is 22.99 g/mole. Determine how many atoms are present in a cube of Na with an edge length of 10 nm. 7. Tantalum and depleted uranium (the uranium left over once the radioactive isotopes are removed) are typically used in penetrators of armor-piercing artillery shells, and these penetrators can often pierce several inches of steel protecting a tank or other armored vehicle. By considering the momentum of a penetrator, briefly describe why Ta and U are preferred for this application rather than, for example, a high-strength steel or an aluminum alloy. 8. Iron (Fe), Cobalt (Co), and Nickel (Ni) are transition metals whose 3d shells are partially filled. Use the spdf notation to describe the electron configuration of each of these. All three have an electronegativity of 1.8. Develop a brief argument why these elements all have the same electronegativity value. 9. Write the electron configurations (spdf notation) characterizing Potassium (K) and Chlorine (Cl). Use these to rationalize the electronegativity of each element. 10. Write the electron configurations (spdf notation) characterizing potassium (K) and bromine (Br). Use these to rationalize the electronegativity of each.
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11. Write the electron configurations (spdf notation) characterizing magnesium (Mg) and iodine (I). Use these to rationalize the electronegativity of each. Would you expect the electronegativity of Mg to be higher, lower, or the same as that of sodium (Na)? Why? 12.
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problems_section_2 - Section 2 Problems Atomic Structure...

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