Atomic orbital is

Step 1: Analyze the question The question asks for the definition of an atomic orbital.

Step 2: Explain the concept In the early Bohr model, electrons were pictured as moving in fixed circular paths called orbits or shells. Modern quantum mechanics showed that we cannot know an electron's exact path. Instead, we describe a region of space where the probability of finding an electron is highest. That region is called an orbital.

• Orbit = a fixed path (old Bohr idea)
• Orbital = a three-dimensional region of high probability of finding an electron (modern idea)

Examples are the s orbital (spherical) and the p orbitals (dumbbell-shaped). Each orbital holds a maximum of 2 electrons.

Step 3: Evaluate the options

• A. A circular path describes an orbit in the Bohr model, not an orbital. Wrong.
• B. A region around the nucleus where electrons are most likely to be found. This is the correct definition of an orbital.
• C. "A path" again describes an orbit. Wrong.
• D. Protons are in the nucleus and do not move around it. Wrong.

Step 4: Answer

Exam tip: Remember "Orbit = Path, Orbital = Probability." If an option uses the word path or circular, it is describing an orbit, not an orbital.