Which of the following is true about semi-conductors
-neither free eletrons nor hoes are considered charge carriers in a semi-conductor
-exposing a crysal of a semiconductor to heat or light starts displacing valence electrons which then move throughout the crystal
-a material is classified as a semiconductor if its resistance to the flow of electric current is too low to permit it to be called a conductor

The statement that is true about semi conductors is this: A MATERIAL IS CLASSIFIED AS A SEMI CONDUCTOR IF ITS RESISTANCE TO THE FLOW OF ELECTRIC CURRENT IS TOO LOW TO PERMIT IT TO BE CALLED A CONDUCTOR.

Semi conductors refers to those materials that can conductor electricity only under suitable conditions, their resistance to the flow of electricity lies between that of conductors and non conductors. Semi conductors are usually used in some electric circuits because the flow of electricity through them can easily be controlled. Examples of semi conductors are silicon, germanium and selenium.

- lead + phosphoric acid = hydrogen + lead(ii) phosphate

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.