Answer:
The number of protons and neutrons.
Explanation:
Neutrons and Protons can't be removed from nucleus from chemical reactions because they are held together super strong and tight. However, nuclear reactions are strong enough to separate them.
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Mole=mass/molecular mass (Mr)
mole=volume/ 22.4
Molecular amount: Mole=amount atoms/ Avogadro's number
Concentration: mole=volume x M
The balanced half-reaction: Cr²⁺⁺(aq) → Cr⁴⁺(aq) + 2e⁻.
Chromium(II) cations two electrons and became chromium(IV) cations.
<span>Oxidation
reaction is increasing of oxidation number of element, because element or
ion lost electrons in chemical reaction.
</span><span>Reduction is lowering
oxidation number because element or ions gain electrons.</span>
D. There must be oxygen added. 2 of them don't even have oxygen anywhere in the formula, and the 3rd loses oxygen, which is reduction.