Lithium has an atomic number of 3 and a mass number of 7. What is the number of protons in a lithium atom?

Rationale

Lithium has 3 protons in its atom.

The atomic number of an element directly indicates the number of protons in its nucleus. Since the atomic number of Lithium is 3, there are 3 protons in a Lithium atom. This proton count remains constant and identifies the element as Lithium on the periodic table.

A (7) YOUR ANSWER

The number of protons in an atom cannot be 7 for Lithium as this directly conflicts with its atomic number of 3. The number 7 actually refers to the mass number of Lithium, which is the sum of protons and neutrons in its nucleus.

B (4) YOUR ANSWER

This answer is incorrect as it doesn't correspond with either the atomic number or the mass number of Lithium. The atomic number, which represents the number of protons in an atom, is 3 for Lithium, not 4.

C (12) YOUR ANSWER

This answer is incorrect because the number 12 is neither the atomic number nor the mass number of Lithium. The atomic number of Lithium, which indicates the number of protons in its nucleus, is 3.

D (3) CORRECT

This choice is correct. As previously mentioned, the atomic number of Lithium is 3, which directly represents the number of protons in the nucleus of a Lithium atom. This count remains invariant across all isotopes of Lithium.

Conclusion

The atomic number of an element is equal to the number of protons in its nucleus. As Lithium has an atomic number of 3, it means there are 3 protons in a Lithium atom. This proton number identifies the element as Lithium on the periodic table and remains constant across all isotopes of the element. All other options provided do not correspond to the atomic number or the proton count of Lithium and are therefore incorrect.

Lithium has an atomic number of 3 and a mass number of 7. What is the number of protons in a lithium atom?

Lithium has 3 protons in its atom.

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