PS 100 - Ch. 21

Locate the elements palladium (Pd, atomic #46) and nickel (Ni, atomic #28) on the periodic table. If Pd is combined with Ni, which of the following characteristics will the product show at room temperature? Select one: a. Non-conducting, transparent solid. b. Shiny, malleable solid. c. Transparent gas. d. Brittle, opaque solid. e. Opaque gas

b. Shiny, malleable solid.

Which of the following is NOT why alloys are useful to us today? Alloys Select one: a. have lower melting temperatures. b. have a higher conductivity rate. c. are less malleable. d. reduce weight in objects.

b. have a higher conductivity rate.

When we increase the temperature of the material A. the conductivity of metals and semi-conductors increase B. the conductivity of metals and semi-conductors decrease C. the conductivity of metals increases whereas that of semi-conductors decreases D. the conductivity of metals decreases whereas that of semi-conductors increases E. the conductivity of semi-conductors does not change

D. the conductivity of metals decreases whereas that of semi-conductors increases

Which of the following is a correct comparison of metals and semi-conductors? Select one: a. Metals have a larger band gap than semi-conductors. b. Metals' resistance increases when temperature increases while a semi-conductors resistance decreases. c. Semi-conductors' molecular orbitals overlap while metals' don't. d. Metals have more valence electrons than semi-conductors. e. Metals have larger electrical resistance than semi-conductors.

b. Metals' resistance increases when temperature increases while a semi-conductors resistance decreases.

Why are metals opaque? Select one: a. because the atoms are closer together than the wavelength of light b. because metals are good conductors c. because metals are malleable d. because metals have high melting and boiling points e. because metals have empty, overlapping orbitals for their electrons

e. because metals have empty, overlapping orbitals for their electrons

Partially filled bands lead to materials that tend to A. be opaque B. be malleable C. conduct heat well D. conduct electricity well E. all of the above

E. all of the above

Metals have higher ionization energies than non-metals do. Select one: T/F

False

When you compare the band gap for a red and a blue LED, what is true? Select one: a. The red LED has the smallest band gap. b. The blue LED has the smallest band gap. c. The band gaps are equal as long as the battery powering them is the same. d. The color of light doesn't have anything to do with the band gap.

a. The red LED has the smallest band gap.