Question

in ____ elements, the outermost shell of an atom contains half the number of electrons needed to complete the shell. it may either borrow or lend electrons.

Explanation:

To solve this, we recall concepts from Chemistry (a subfield of Natural Science) about electron shells and element behavior. Elements where the outermost shell has half the electrons needed to complete it (and can either gain or lose electrons) are typically "metalloid" or more precisely, considering the electron configuration logic, the term here is related to elements with such a valence electron situation. Wait, actually, the key is that in "metalloid" or more accurately, the group of elements where the outermost shell has half the required electrons (like elements that can act as both donors and acceptors, e.g., some metalloids or transition - like, but more precisely, the term for elements with this electron - shell property is "metalloid" is not accurate. Wait, the correct term here is "semi - metallic" or more precisely, the elements in question are "metalloids" but actually, the answer is "metalloid" or more accurately, the term is "metalloid" elements? Wait, no, let's think again. The outermost shell having half the electrons needed to complete it. For example, elements with 4 valence electrons (since a full shell for some is 8, half is 4) like carbon, silicon, germanium etc. These are metalloids. So the blank should be filled with "metalloid".

Answer:

metalloid