How does band theory explain why a crystal made of carbon atoms (i.e. diamond) is transparent, while a crystale made of aluminum atoms is not?
The answer lies in the band structure of the two materials. The band structure describes how the electrons in a solid are bound, and what other energy states are available to them.
the band gap for transparent diamonds is very wide as shown
Normally, diamond is not a conductor: all the electrons live in
the "valence band", and you need a photon with at least 5.4 eV of
energy to push an electron into the conduction band. In the
process, that photon would be absorbed. A photon with less energy
cannot give its energy to an electron, because that electron "has
nowhere to go". And since visible light has energies of between
1.65 and 3.1 eV, only UV photons have enough energy to be absorbed
by pure diamond.
Normally, diamond is not a conductor: all the electrons live in the "valence band", and you need a photon with at least 5.4 eV of energy to push an electron into the conduction band. In the process, that photon would be absorbed. A photon with less energy cannot give its energy to an electron, because that electron "has nowhere to go". And since visible light has energies of between 1.65 and 3.1 eV, only UV photons have enough energy to be absorbed by pure diamond.
In the case of aluminium the gap between balance band is less or overlapped some time.
And visible light has much more more energy to get trasition of electron and which cause photon to absorb and make it not to appear transparent.
How does band theory explain why a crystal made of carbon atoms (i.e. diamond) is transparent, while a crystale made of aluminum atoms is not?
Explain why Carbon Dioxide is a gas at room temperature while a diamond is a solid even though they both have covalent bonds.
Utilizing band theory, explain how p-type and n-type semiconductors are made, and show how they work in a diode.
Utilizing band theory, explain how p-type and n-type semiconductors are made, and show how they work in a diode
explain why the molar enthalpy of formation for Carbon Graphite, is 0 kj/mol, while the molar standard enthalpy of formation for carbon diamond, is +1.90 kj/mol and that of carbon gas is +716.7 kj/mol.
Why does ice float on liquid water? It is a compound without carbon atoms that exists in the liquid state at room temperature and pressure. The linear structure of the water molecule allows ice molecules to pack together tightly enough to allow ice to float. Water molecules in the solid form are held in a crystal pattern that has voids between the molecules. Ice is structurally similar to wood, so ice floats on water in a manner similar to wooden...
QUESTION 19 0.5 points Describe: How does "evolutionary theory" explain why death is necessary_in cells (and people)? TTT Arial 3 (12pt) TEE 5. Words:0 Path:p
1a. How does kinetic molecular theory explain why pressure is directly propirtional to temperature at a fixed volume? 1b. Explain Boyle’s Law using the Kinetic Molecular Theory. 1c. A hot air balloonist is rising too fast for her liking. should she increase or decrease the temperature of the gas in the balloon? 1d. Could the pilot of the balloonist from (1c) reduce her rate of ascent by allowing some gas to leak out of the balloon?
How does the theory of cultural materialism help explain the Awlad' Ali Bedouin marriage and kinship system, as discussed in the lecture? Why does the kinship system support the infrastructure? How does the super structure (belief system) support the kinship system?
Q1 Explain how an op amp works (i.e. how does an amplifier of near infinite (extremely high) amplification create a gain of much less (i.e. 2 or 3 or 4) with just the resistors. Q2 Do we always use negative feedback? Why? Q3 What would happen if we used positive feedback? Q4 Regarding the inputs what is the advantage of a non-inverting amplifier?
1. Consider unknown compounds made of C, H and O atoms. Explain how you expect the water solubility of a compound to change as it's weight percent oxygen increases. 2. What is the advantage of using a mixed melting point analysis to identify a compound? Does your mixed melting point value identify your isolated material as cholesterol?