How many atoms are in 3 moles of nitrogen

1 mol of Mg(NO3)2 contains 6.022*10^23 molecules

3 mol Mg(NO3)2 contains 3*6.022*10^23 = 1.81*10^24 molecules

Each Mg(NO3)2 molecule contains 2 N atoms  

Number of N atoms = 2*1.81*10^24 = 3.62*10^24 N atoms.

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.

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