Which term describes an element that possesses some properties of both metals and non-metals?

The correct term that describes an element exhibiting properties of both metals and non-metals is "metalloid." Metalloids are elements that typically have a metallic luster but are brittle and not malleable, which distinguishes them from metals. They can conduct electricity better than non-metals but not as well as metals, making them semiconductors. This unique combination of characteristics allows metalloids to be utilized in various applications, particularly in the electronics industry for creating semiconductors.

The other terms listed refer to specific categories of elements: alkali metals are a group of highly reactive metals located in Group 1 of the periodic table; noble gases are a group of inert gases in Group 18 known for their lack of chemical reactivity; and transition metals refer to the d-block elements that exhibit typical metallic properties, such as malleability and conductivity. None of these categories encapsulate the mixed characteristics of both metals and non-metals like metalloids do.