That is, two electrons per atomic orbital, each with a different spin.
As shown at Schrödinger equation solution for the helium atom, they do repel each other, and that affects their measurable energy.
However, this energy is still lower than going up to the next orbital. TODO numbers.
This changes however at higher orbitals, notably as approximately described by the aufbau principle.
Fresnel diffraction Updated 2025-07-16
Near field approximation to Kirchhoff's diffraction formula, i.e. when the plane of observation is near the object diffracting.
Lamp Updated 2025-07-16
Matter.js Updated 2025-07-16
To run the demos locally, tested on Ubuntu 22.10:
git clone https://github.com/liabru/matter-js
cd matter-js
git checkout 0.19.0
npm install
npm run dev
and this opens up the demos on the browser.
GitHub Updated 2025-07-16
This is where Ciro Santilli stored his code since he started coding nonstop in 2013.
He does not like the closed source aspect of it, but hey, there are more important things to worry about, the network effect is just too strong.
Hydrogen 1-2 spectral line Updated 2025-07-16
Equation "Hydrogen spectral series mnemonic" gives for example from principal quantum number 1 to 2 a difference:
which with Planck-Einstein relation gives about 121.6 nm ( Hz), which is a reasonable match with the value of 121.567... from the NIST Atomic Spectra Database.
Intel Xe Updated 2025-07-16
Megahertz Updated 2025-07-16
Mega-Hertz, i.e. a million Hertz.

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