Which quantity represents the number of protons in an atom?
(a) atomic number
(b) oxidation number
(c) number of neutrons
(d) number of valence electrons
Answer (3)
The answer is (a) atomic number
Atomic number = no. of protons = no. of electrons
The atomic number is equal to the number of protons in an element. The oxidation number and valence electrons can vary depending on whether it is an ion or not. The number of neutrons can also vary depending on what isotope the atom is. However, the number of protons cannot be changed without changing the identity of the base atom itself.
The atomic number represents the number of protons in an atom. For example, an atom of oxygen with an atomic number of 8 contains 8 protons. Therefore, the correct answer to the question is (a) atomic number.
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