ch 21 unit 3 physical science

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.

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.

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.

If GaAs forms a semiconductor like Ge, which of the following elements will form a semiconductor like Si?

Al and P

Compounds between two different metals are called

Alloys

Metals do not let light through.

true

Metals have a greater tendency than non-metals do lose electrons.

true

A metal is..

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

Why are alloys useful to us today?

a. have lower melting temperatures. c. are less malleable. d. reduce weight in objects.

Which of the following is NOT a characteristic of a metal or alloy? Select one: a. Electrically Conductive b. Thermally Conductive c. Malleable d. Brittle

d. brittle

Current can flow in all directions in an LED?

false

Metals have higher ionization energies than non-metals do.

false

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

false