Chapter 3, Problem 91AE

Very small semiconductor crystals, composed of approximately 1000 to 10,000 atoms, are palled quantum dots. Quantum dots made of the semiconductor CdSe are now being used in electronic reader and tablet displays because they emit light efficiently and in multiple colors, depending on dot size. The density of CdSe is 5.82 g/cm³

a. What is the mass of one 2.5-nm CdSe quantum dot?

b. CdSe quantum dots that are 2.5 nm in diameter emit blue light upon stimulation. Assuming
that the dot is a perfect sphere and that the empty space in the dot can be neglected,
calculate how many Cd atoms are in one quantum dot of this size.

c. What is the mass of one 6.5-nm CdSe quantum dot?

d. CdSe quantum dots that are 6.5 nm in diameter emit red light upon stimulation. Assuming that
the dot is a perfect sphere, calculate how many Cd atoms are in one quantum dot of this size.

e. If you wanted to make one 6.5-nm dot from multiple 2.5-hm dots, how many 2.5-nm dots
would you need, and how many CdSe formula units would be left over, if any?