A substance where almost all have the same atomic number of protons
Answer: the mass number is 51.9961 u.
Explanation: Basically your looking for the mass number of a ATOM of chromium now if you where looking for chromium and not the atom it's self it would be a different number which is 52-54
The correct answer to complete the sentence is C. <span>The combination of two or more atoms, from the same or different elements, creates a molecule.</span><span> Compounds
are a type of molecules made of atoms from different elements held together by chemical
bonds.</span>
Every part helps an organism living in it survive