In the atomic symbol _{17}^{35}Cl_, which number represents the atomic number and which represents the mass number?

• A. Both 17 and 35 are mass numbers.
• B. 17 is the atomic number; 35 is the mass number.
• C. 35 is the atomic number; 17 is the mass number.
• D. Both 17 and 35 are atomic numbers.

Answer: (B)

Verified step by step guidance

1. Understand the notation of an atomic symbol, which is generally written as \(_{Z}^{A}X\), where \(X\) is the chemical symbol, \(Z\) is the atomic number, and \(A\) is the mass number.
2. Recall that the atomic number (\(Z\)) represents the number of protons in the nucleus of the atom and defines the element.
3. Recognize that the mass number (\(A\)) is the total number of protons and neutrons in the nucleus.
4. In the given symbol \(_{17}^{35}Cl\), the subscript 17 is the atomic number, indicating chlorine has 17 protons.
5. The superscript 35 is the mass number, meaning the total number of protons and neutrons in this chlorine isotope is 35.