(C) Electron cloud
the electron cloud is formed by all the electrons in the atom
Dmitri Mendeleev, he realized that the physical and chemical properties of elements were related to their atomic mass and arranged them into groups (columns)
Answer:
Helium has atomic mass 4.002602.
So the answer to yr question is helium.
Metalloids are metallic-looking brittle solids<span> that are either semiconductors or exist in semiconducting forms, and have amphoteric or weakly acidic oxides. Typical </span>nonmetals<span> have a </span>dull<span>, coloured or colourless </span>appearance<span>; are </span>brittle<span> when </span>solid<span>; are poor conductors of heat and electricity; and have acidic oxides.</span>