Lithium atomic no. is 3 and their also electrons and protons are 3 but

1.	Lithium atomic no. is 3 and their also electrons and protons are 3 but neutrons is 4. why??
Answer» tion:That is because the lithium ATOM always has 3 PROTONS, the atomic number for lithium is always 3. The mass number, however, is 6 in the isotope with 3 NEUTRONS, and 7 in the isotope with 4 neutrons.ISOTOPES are elements with same atomic number but Isotopes are elements with same atomic number but DIFFERENT atomic mass number

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