Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.
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Question: molar mass is the mass of a substance that has 6.022 × 10 atoms (avogadro's number).

Answer: molar mass


Question: area code 701 is an area code for the u.s. state of north dakota.

Answer: area code 701


Question: the alkaline earth metals are the second group of metals on the periodic table.

Answer:
alkaline earth metal