When filling degenerate orbitals, electrons fill them singly first, with parallel spins is known as When filling degenerate orbitals, electrons fill them singly first, with parallel spins is known as:

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

Answer : The correct option is, (A) Hund's rule

Explanation :

Hund's rule : It states that the electrons are singly filled first in each orbital having same spin, then only pairing occurs.

Heisenberg  uncertainty principle : It is defined as the position and the momentum both can not be determined simultaneously.

Aufbau principle : It states that the atom or ion that present in the ground state, the lowest energy level will be filled first before occupying the higher levels.

Pauli Exclusion Principle : It states that no two electrons present in an atom or a molecule can have the same set of the four quantum numbers.

Hence, the correct option is, (A) Hund's rule

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).

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