The atoms of $^{64}_{29}$Cu and $^{65}_{30}$Zn have the same number of?

Analyze the question: We are comparing two atoms, Cu-64 (atomic number 29, mass number 64) and Zn-65 (atomic number 30, mass number 65). We need to find which particle count is the same in both.

Concept:

• Mass number (A) = number of nucleons (protons + neutrons)
• Atomic number (Z) = number of protons = number of electrons (in a neutral atom)
• Neutrons = A − Z

Solution:

| Atom | Protons | Electrons | Neutrons (A − Z) | Nucleons | |------|---------|-----------|------------------|----------| | ⁶⁴₂₉Cu | 29 | 29 | 64 − 29 = 35 | 64 | | ⁶⁵₃₀Zn | 30 | 30 | 65 − 30 = 35 | 65 |

Checking each option:

• A. Nucleons: 64 vs 65, not the same.
• B. Electrons: 29 vs 30, not the same.
• C. Neutrons: 35 vs 35, the same.
• D. Protons: 29 vs 30, not the same.

The two atoms are called isotones: atoms of different elements with the same number of neutrons.

Tip: Remember the three "iso" words:

• Isotopes: same protons (same element), different neutrons
• Isobars: same mass number, different protons
• Isotones: same neutrons, different protons

When a question gives two different elements with mass numbers and atomic numbers close together, calculate A − Z for each and check for isotones.