Cr2(CO3)3 is Chromium (III) Carbonate or Chromic Carbonate.
It is composed of Chromium, Carbon, and Oxygen. Chromium has 2 atoms, Carbon has 3 atoms, and Oxygen has 9 atoms.
This compound is composed of 36.6% Chromium, 12.7% Carbon, and 50.7% Oxygen.
The answer is Noble gas because they have a full octet
Protons and neutrons are in the nucleus of an atom, whereas electrons are present in orbitals, or shells, outside an atom. Electrons are negatively charged, protons positive, and neutrons have no charge, or are neutral. Protons and neutrons have a relative mass of approx. 1 Atomic Mass Unit (amu), whereas electrons have a relative mass of approx 0.00055 amu.