The scientific law of conservation of mass states that the total amount of mass in an isolated system remains constant. this means that the atoms present before a reaction are still present at the end of a reaction, they are just rearranged to form a new molecules and compounds. this is a scientific law becuse

It is a statement based on repeated experiments and observations, that assures its veracity.

Explanation:

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In this case, a raft of experiments and observations were previously carried out and analyzed in order to substantiate whether the mass remains constant when a chemical reaction is undergone into an isolated system. This, in addition to the given conclusion, led to a scientific law as the law of conservation of mass is considered as a statement that came up from repeated experiments and observations in which a repeatable behavior of matter assured its veracity over a wide range of similar conditions.

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it is stable as it is in group 0 which have full outer shells of electrons