Lesson 21

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

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

When you compare the band gap for a red and a blue LED, what is true?

The red LED has the smallest band gap.

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

Al and P

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

have a higher conductivity rate but they are useful because they have lower melting temperatures, are less malleable and reduce weight in objects.

What happens to the number of MO's as the number of atoms that come together increases?

increases

Which type of atom has valence electron states high enough in energy that they overlap with the stacked together molecular orbitals that form the conduction band?

metal

Which type of atom has valence electrons higher in the energy well?

metal

Which type of atom has the highest ionization energy?

non-metal

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

Why are metals opaque?

because metals have empty, overlapping orbitals for their electrons

What happens to the spacing between the energy of one MO and the next one immediately above or below it as the number of atoms that come together increases?

decreases

Current can flow in all directions in an LED.

false

Metals have higher ionization energies than non-metals do

false