What Happens When an Atom Gains or Loses Energy? Energy Levels

What happens when an atom gains or loses energy? The answer is written in light. Electrons in an atom can only have certain allowed energy levels, like the steps of a staircase. Absorb a photon with exactly the right energy and an electron jumps up (excitation); drop back down and the atom emits a photon whose energy equals the gap (emission). That's why glowing hydrogen shows only a few sharp lines, like the red H-alpha line at 656 nm (about 1.9 eV), and why every element has its own spectral fingerprint. We also dive into the nucleus: excited nuclei release gamma rays carrying around a million electron volts, far more than visible light. Plus: how helium was discovered in sunlight in 1868, and where fireworks, sodium lamps, neon signs and LEDs get their colours. ⚛️ A new NuclearVerse episode every day. Subscribe to AtomX:    / @atomx-2   📚 Helpful for Class 11 & Class 12 Physics. #Class11Physics #Class12Physics Chapters: 0:00 What happens when an atom gains or loses energy? 0:17 Quiz 1: why hydrogen glows in only a few colours 0:33 Energy levels: a staircase, not a ramp 0:45 Absorption, excitation and emission 1:14 Quiz 2: which photon carries the most energy? 1:34 Hydrogen red line: 1.9 eV, 656 nm 1:47 Nuclear energy levels and gamma rays 2:21 Quiz 3: how helium was discovered 2:41 Fireworks, neon signs and LEDs 2:53 Recap ◀ Previous: Ep 18, E=mc² Explained: How Much Energy Is Hidden Inside Matter?:    • What Is E=mc²? Einstein's Equation Explain...   📺 NuclearVerse playlist:    • NuclearVerse: Nuclear Physics Explained   Sources: NIST Atomic Spectra Database (hydrogen H-alpha 656.3 nm); NIST CODATA (eV, Planck constant); Royal Society of Chemistry / Britannica (discovery of helium, 1868 & 1895); IAEA / HyperPhysics (nuclear gamma decay energies). 3D animations are conceptual visualizations, not to scale. 📲 Follow AtomX: X https://x.com/AtomX_universe · Telegram https://t.me/AtomX_2 #EnergyLevels #AtomicSpectra #NuclearVerse