A mole is defined as the number of atoms in an exact mass of which isotope?

Isotope of carbon-12.

Explanation:

The MOLE  is a unit of measurement of the amount of a pure substance which contains exactly the same number of chemical units which could be (Atoms, molecules etc.) posses atoms in exactly grams of isotope of carbon-12 (i.e., ).

So, The mole is the Notation  used for an amount  as same the 12 number is used for dozen for making count of Bananas and many more.

The is known as the fundamental constant names Avogadro's number (), It is in the honor of Italian scientist Amedeo Avogadro.

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