Here's why:
* Electron affinity is the change in energy when an electron is added to a neutral atom or molecule in its gaseous state to form a negative ion.
* A positive electron affinity means that energy is released when an electron is added, making the process favorable.
* Diamond is a wide band gap semiconductor with a very strong carbon-carbon bond. This makes it difficult for an electron to be added to the lattice, as it would require overcoming the strong bond energy.
Therefore, diamond exhibits a positive electron affinity because it requires energy to add an electron, making it an unfavorable process.
