It is a column of elements in the periodic table of the chemical elements.
Answer:

Explanation:
A protein is a long chain of amino acids linked together by amide groups.
The general structure is
![\rm \left[-NHCHR-\underbrace{\hbox{CO-NH}}_{\hbox{amide group}}-CHRCO-\right]_{n}](https://tex.z-dn.net/?f=%5Crm%20%5Cleft%5B-NHCHR-%5Cunderbrace%7B%5Chbox%7BCO-NH%7D%7D_%7B%5Chbox%7Bamide%20group%7D%7D-CHRCO-%5Cright%5D_%7Bn%7D)
Answer: Fe2O3
Explanation:
5.60 g Iron Oxide
- 3.92 g Iron
===========
= 1.68 g Oxygen
Convert Fe and O to moles:
3.92 g Iron/55.85 = 0.0702 moles Fe
1.68 g Oxygen/16 = 0.105 moles O
The ratio of O to Fe is 1.50. There are 3/2 O for each Fe. Multiply by 2 to get whole numbers: 2Fe for every 3O: Fe2O3