3. Because atoms are so small,

Answer"

because atomic radii are so small they are expressed in a unit that is more convient for the size of atoms, this unit is called picometer. another unit is called the unified atomic mass unit and is used to express the mass of atoms.

Explanation:

answer:

the reaction is type of combination reaction.

explanation:

on the product side, there are 2 molecules of bonded to fe   which means one atom of fe are combined two molecules of . so, balanced chemical equation becomes :

this reaction follows the reaction type of combination reaction. a combination reaction is defined as chemical reaction in which reactants combines together to form a single product.