If lithium has an atomic number of 3 and a mass number of 7, the correct number of protons, neutrons, and electrons, respectively, is:

Atom is the smallest unit of the matter consist the positive charged nucleus and the electrons which moves around it. The atom can not be divided further.

The atom of a matter is made by three elements-

1) Neutron-Neutron is the element of atom, which has zero charge. The total number of the neutrons in an atom is the difference of mass number of the atom and its atomic number.
2) Proton-Proton is the element of atom, which has positive charge. The atomic number of the atom is equal to the number of proton of the atom.
3) Electron-Electron is the element of atom, which has negative charge. The number of proton is equal to the number of electron for a neutral atom.

The atomic number of the atom is equal to the number of proton of the atom, and the atomic number of the lithium is 3. Thus, the number of proton is,

[tex]p=3[/tex]

The lithium has an atomic number of 3 and a mass number of 7. Thus, the number of neutron is,

[tex]n=7-3\\n=4[/tex]

The number of proton is equal to the number of electron for a neutral atom. Thus, the number of electron in lithium is,

[tex]e=p\\e=3[/tex]

Hence, the total number of protons, neutrons, and electrons of lithium atom is 3, 4 and 3 respectively.

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