Consideting the definition of compound, the correct answer is second option: Carbon, hydrogen and chlorine atoms combine chemically, forming compounds.
A compound is any substance formed by the union of two or more types of chemical elements, linked together by chemical bonds.
In other words, A chemical compound is the substance that results from the combination of two or more different chemical elements linked under a certain arrangement and in certain proportions.
Each compound has a chemical name (which responds to certain nomenclature rules) and a formula that indicates the elements it is composed of and the number of atoms each contains.
Then, the correct answer is second option: Carbon, hydrogen and chlorine atoms combine chemically, forming compounds.
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