Which number is used to uniquely identify an atom of a particular element?

• A. Atomic number
• B. Avogadro's number
• C. Quantum number
• D. Mass number

Answer: (A)

Verified step by step guidance

1. Understand that atoms of different elements are distinguished by a specific number that identifies the element uniquely.
2. Recall that the Atomic number (symbolized as \(Z\)) represents the number of protons in the nucleus of an atom.
3. Recognize that the Atomic number determines the identity of the element because each element has a unique number of protons.
4. Note that the Mass number is the total number of protons and neutrons, which can vary for isotopes of the same element and thus does not uniquely identify the element.
5. Understand that Avogadro's number is a constant used to count particles (atoms, molecules) and Quantum numbers describe electron properties, so neither uniquely identifies an element.