The requirements for one type of atom to substitute for another in a solid solution are:.A. All substitutions must be limited to the same element. B. An atom must be identical in size. C. An atom must be similar in size. D. The substituting atom must be from the same period. E. The substituting atom must be from the same group.

E. The substituting atom must be from the same group.

Explanation:

Usually members higher-up in the group can replace or substitute lower members of a group

n+h→nh3

we must remember that nitrogen and hydrogen are both diatomic molecules in their standard gas form. this adjusts the equation to

n2+h2→nh3

now we need to adjust coefficients in order to balance the atoms on each side of the equation. currently we have 2 atoms of nitrogen and 2 atoms of hydrogen on the reactant side and 1 atom of nitrogen and 3 atoms of hydrogen on the product side.

we can balance the hydrogens by placing a coefficient of 2 in front of ammonia and a coefficient of 3 in front of the hydrogen.

n2+3h2→2nh3

this gives us 6 hydrogen on each side and coincidentally the nitrogens now equal 2 on each side.

first one is the correct answer