Question

which of the following is a soft metal and the lightest element that is a solid at standard temperature and pressure? (1 point)
○ cobalt
○ silica
○ silicon
○ lithium

Explanation:

To solve this, we analyze each option:

• Cobalt: A hard metal, not the lightest solid - metal candidate here.
• Silica: It is $\ce{SiO_2}$, a non - metal compound (a mineral), not a metal.
• Silicon: A metalloid, not a metal.
• Lithium: It is a soft metal. Among solid elements at standard temperature and pressure (STP), lithium has a very low density (it is the lightest solid metal at STP).

Answer:

D. lithium