# What were the contributions of de Broglie, Hund, and Pauli to our understanding of the atom?

Jul 7, 2017

See below.

#### Explanation:

de Broglie - particle-wave duality

Showed that electrons can act as waves, where their wavelength is inversely proportional to the electron's momentum,

$\lambda = \frac{h}{p}$,

where:

• $\lambda$ = de Broglie wavelength in $m$
• $h$ = Planck's constant ($6.626 \cdot {10}^{-} 34 J \cdot s$)
• $p$ = electron's momentum in $k g \cdot m / s$

Hund - Hund's rule of maximum multiplicity

An orbital in a subshell tends to fill with one electron before it gets two electrons, and these electrons in singly occupied orbitals ought to have the same spin.

[NOTE: exceptions occur when the orbitals get big enough.]

Pauli - Pauli's exclusion principle

Two electrons in the same orbital cannot have the same set of four quantum numbers:

• principal quantum number ($n$)
• orbital angular momentum quantum number ($l$)
• magnetic quantum number (${m}_{l}$)
• spin quantum number (${m}_{s}$).

If both were to reside in the same orbital, they automatically have 3 identical quantum numbers, so their spins must be opposite.