Atomic Physics

Step 1: Recognizing the isotopic notation.
The notation refers to carbon-12, where: - 12 is the mass number (sum of protons and neutrons), - 6 is the atomic number (number of protons).
Step 2: Conclusion.
The isotope represented by is carbon-12, making option (A) the correct answer.

Step 1: Understanding the energy levels of hydrogen atom.
In a hydrogen atom, the energy of the electron in a given level is given by the equation: where is the principal quantum number.
Step 2: Calculating the energy for other levels.
For the first excited state (n=2), the energy is . Similarly, for higher levels, the energy can be calculated.
Step 3: Conclusion.
The possible energies for the electron in different levels are and , which makes option (B) correct.