Which is the correct isotope symbol for an atom with 42 protons and 49 neutrons?

• A. Tc-91
• B. Mo-49
• C. Mo-91
• D. Ru-91

Answer: (C)

Verified step by step guidance

1. Identify the element by its number of protons. The atomic number (Z) is equal to the number of protons, so here Z = 42.
2. Use the periodic table to find the element with atomic number 42. This element is Technetium (Tc).
3. Calculate the mass number (A) by adding the number of protons and neutrons: \(A = Z + N = 42 + 49\).
4. Write the isotope symbol in the form \(^{A}_{Z}\text{Element}\) or as Element-A, where A is the mass number and the element symbol corresponds to atomic number 42.
5. Compare the calculated isotope symbol with the given options to determine which one correctly represents the atom with 42 protons and 49 neutrons.