Which of the following is the correct nuclear symbol for the isotope of potassium with mass number 40?

• A. ^{40}_{18}K
• B. ^{40}_{20}K
• C. ^{40}_{19}K
• D. ^{19}_{40}K

Answer: (C)

Verified step by step guidance

1. Understand that the nuclear symbol for an isotope is written as \(^{A}_{Z}X\), where \(A\) is the mass number (total number of protons and neutrons), \(Z\) is the atomic number (number of protons), and \(X\) is the chemical symbol of the element.
2. Identify the element potassium (K) on the periodic table to find its atomic number \(Z\). Potassium has an atomic number of 19, meaning it has 19 protons.
3. Recognize that the mass number \(A\) is given as 40, which represents the sum of protons and neutrons in the nucleus.
4. Combine the atomic number and mass number with the element symbol to write the nuclear symbol correctly as \(^{40}_{19}K\).
5. Verify that the other options are incorrect because either the atomic number does not match potassium's atomic number (19) or the mass number is misplaced.