Question

"It is impossible to determine simultaneously the exact position and exact momentum of an electron." This statement is called

• A. Pauli's exclusion principle
• B. Hund's rule
• C. Aufbau rule
• D. Heisenberg uncertainty principle

Hint:

Because of Heisenberg's Uncertainty Principle, Bohr's old concept of electrons traveling in well-defined, exact circular "orbits" had to be completely discarded and replaced with the concept of probability "orbitals"!

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question provides a foundational quotation from quantum mechanics and asks for the name of the principle it defines.

Step 2: Detailed Explanation:
Let's review the fundamental rules of quantum atomic structure:
Pauli's exclusion principle: States that no two electrons in a single atom can have the exact same set of all four quantum numbers. (It essentially means an orbital holds a max of 2 electrons with opposite spins).
Hund's rule of maximum multiplicity: States that electron pairing in degenerate orbitals will not occur until each orbital is singly occupied with parallel spin.
Aufbau principle: States that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels.
Heisenberg's Uncertainty Principle: Formulated by Werner Heisenberg, it states that it is physically and fundamentally impossible to determine simultaneously both the exact position ($\Delta x$) and exact momentum ($\Delta p$) of a microscopic, moving particle like an electron with absolute certainty. The mathematical relationship is defined as $\Delta x \cdot \Delta p \ge \frac{h}{4\pi}$.

Step 3: Final Answer:
The statement is the Heisenberg uncertainty principle, matching option (d).