Answer:
I'm sure it's option A. Cast Fossil
The Curies discovered radium
<span>The molecular mass of sodium oxide (Na2O) is A. 61.97894. The molecular mass of a molecule (Mr) is the sum of atomic masses of its atoms (Ar). The molecular mass of sodium oxide is: Mr(Na2O) = 2 * Ar (Na) + Ar(O). From the periodic table, Ar(Na) = 22.989769 and Ar(O) = 15.9994. The molecular mass of sodium oxide is: Mr(Na2O) = 2 * 22.989769 + 15.9994 = 45.979538 + 15.9994 = 61.97894.</span>
Carbon 12 and carbon 14 are two isotopes of the elements carbon.the difference between carbon 12 and carbon 14 is the number r of neutrons in each atom.the number given after the atom name (carbon) indicates the numbers of protons plus neutron is an atom or iron. Atom of both isotopes of carbon contain 6 protons
The answer is the third choice because is oxidation half reactions, only the oxidation state of the reducing agent changes; in this third choice, Fe2+ is oxidized and becomes Fe3+. Just keep in mind that half reactions usually include the change in electrons:
Fe2+ -> Fe3+ +e-<span />