Silicon crystals are semiconductors. Which of the following is a correct reason for the increase in the conductivity of Si cryst
als when a small fraction of Si atoms are replaced with those of a different element?a. P atoms introduce additional mobile negative charges.b. P atoms introduce additional mobile positive charges.c. Ge atoms have more electrons than Si atoms.d. Ge atoms are much smaller than Si atoms.
1 answer:
Answer:
a. P atoms introduce additional mobile negative charges
Explanation:
Silicon atoms have a<u> valency </u>of 4, this means that there are 4 electrons in their outermost orbital. Thus, in silicon crystals, each Si atom is connected to 4 different Si atoms.
When we replace a few of these Si atoms with P atoms, which have a valency of 5, 4 out of these 5 outermost electrons will be bonded with the surrounding Si atoms. The fifth electron would not be bonded, meaning it would be free to move, acting as a mobile negative charge carrier (See the picture below).
Just to be clear, regarding option c), it's true that Ge atoms have more electrons that Si atoms, however that it's not a reason for an increase in conductivity.
You might be interested in
Answer : The enthalpy change during the reaction is -6.48 kJ/mole
Explanation :
First we have to calculate the heat gained by the reaction.
where,
q = heat gained = ?
m = mass of water = 100 g
c = specific heat =
= final temperature =
= initial temperature =
Now put all the given values in the above formula, we get:
Now we have to calculate the enthalpy change during the reaction.
where,
= enthalpy change = ?
q = heat gained = 23.4 kJ
n = number of moles barium chloride =
Therefore, the enthalpy change during the reaction is -6.48 kJ/mole