What best explains the observed trend in atomic radii going down the periodic table

As we move from top to bottom, the y-value which is the Atomic Radii of the element tends to increase.

Explanation:

By adding more shells the atom gets bigger because  the electrons get further away creating more space, distance from the nucleus increases.

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.