This shows which isotope of lead it is by giving the atomic mass of that particular isotope of lead. While lead and all elements always have the same number of protons as every other atom of that element, this number allows you to determine the number of neutrons the lead has, which can vary. To find the number of neutrons, take the 214 and subtract from the number of protons in lead.
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Lead-214 is an isotope. It represents the number of electrons and protons. You can find the number of neutrons by subtracting the protons from the mass number.
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It represents the atomic number.