Where do band gaps open?
- At zero energy always
- Outside the crystal
- At zone edges via Bragg reflection
What happens to atomic levels in a crystal?
- They spread into bands with gaps between
- They stay single and unchanged
- They become random noise energies
A completely full top band conducts electricity well.
Circle one: True False
Which filling makes an insulator?
- A full band plus a large gap
- A half empty top band
- Zero atoms in the sample
Which filling makes a metal?
- A full band with a large gap
- A partly filled or overlapping top band
- No electrons at all
What is a semiconductor?
- A small-gap insulator crossed by heat or light
- An infinitely gapped wall
- A metal with dark paint
Two similar crystals differ in conduction. A student says structure alone decides. What is wrong?
- Crystals never conduct at all
- Gaps never open in similar structures
- Filling and gap size decide alongside structure
What is the free electron gas in band language?
- Bands with doubled gaps
- The picture with gaps switched off
- An insulator with extra paint
Why some solids conduct W1-mt_9f74Vu6qnW-s1
- At zone edges via Bragg reflection · Bouncing at the zone edge splits travelling waves in energy.
- They spread into bands with gaps between · A mole of atoms turns each level into a band.
- False · No nearby empty spots means electrons cannot respond.
- A full band plus a large gap · Full plus gapped strands every electron.
- A partly filled or overlapping top band · Room to gain energy means room to move.
- A small-gap insulator crossed by heat or light · Small gaps let a few electrons hop across.
- Filling and gap size decide alongside structure · Looks match while fillings and gaps differ.
- The picture with gaps switched off · Ignoring the ions removes the bounce that opens gaps.