Which of the following species has 28 protons and 26 electrons?

• A. Cu^{2+}
• B. Ni^{2+}
• C. Ni
• D. Fe^{2+}

Answer: (B)

Verified step by step guidance

1. Identify the atomic number of each element, which corresponds to the number of protons. Copper (Cu) has 29 protons, Nickel (Ni) has 28 protons, and Iron (Fe) has 26 protons.
2. Determine the number of electrons for each species by considering their charge. For a cation, subtract the charge from the number of protons. For example, for Cu^{2+}, electrons = protons - 2.
3. Calculate the number of electrons for each species: Cu^{2+} has 29 - 2 = 27 electrons, Ni^{2+} has 28 - 2 = 26 electrons, Ni (neutral) has 28 electrons, and Fe^{2+} has 26 - 2 = 24 electrons.
4. Compare the number of protons and electrons for each species to find which one has 28 protons and 26 electrons.
5. Conclude that the species with 28 protons and 26 electrons is Ni^{2+}.