WHY NATURE FORM A NEW SUBSTANCE
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chemical reaction happens when substances break apart or combine to form one or more new substances. New substances form when bonds break and new bonds form. The chemical properties of the new substances are different from those of the original substances. . Some chemical reactions produce a precipitate.

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a

b) nuclear ive learned that in a pedtrodic table