Question 9

substances that conduct an electric current only under certain conditions are most likely to be

a)metals

b)nonmetals

c)metalloids

d)noble gases

The substance is C) Metalloids.

Metalloids are semiconductors since they are neither great nor poor conductors of electricity as they conduct it only under certain conditions.

Due to presence of free electron in the atomic structures of metals, they are considered as best as well as good conductors of electricity. On the other hand, due to absence of free electron, they cannot conduct electricity thus nonmetals are poor conduits of electricity.  

Metalloids have the properties of the two nonmetals and metals. Their electronic structures are moderate between those of metals and nonmetals. Thus, they have the ability to direct electricity only under some conditions.