Iron reacts with atmospheric oxygen to form iron oxide or ferric oxide. Look at the chemical equation for this reaction: Fe + O2 → Fe2O3

This equation is unbalanced. Which of the following is the correct balanced equation for this reaction?

A.
4Fe + 3O2 → 2Fe2O3
B.
3Fe + 4O2 → 2Fe2O3
C.
2Fe + 4O2 → 3Fe2O3
D.
3Fe + 3O2 → 4Fe2O3
E.
4Fe + 4O2 → 3Fe2O3

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.