PHY S 100 Lesson 21

If a certain LED (doped semi-conductor) is cooled in liquid nitrogen, the color moves to a higher frequency. What happens to the band gap?

It increases in energy.

Metals have a greater tendency than nonmetals to lose electrons.

True

A metal can best be described as

a network solid consisting of positively charged atoms in a sea of electrons.

Which of the following is not why alloys are useful to us today?

Alloys have a higher conductivity rate.

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?

shiny, malleable solid

Light can only be seen through very thin metal.

False

Metals have higher ionization energies than nonmetals do.

False

The energies of the orbitals that form when metals interact are very widely spaced in energy.

False

Which of the following is a correct comparison of metals and semi-conductors?

A metal's resistance increases when temperature increases while a semi-conductor's resistance decreases

What are compounds between two different metals called?

alloys

Which of the following is not a characteristic of a metal or alloy?

brittle