Understanding the scientific rationale behind Selenium's position in the periodic table:
Belongs to Group 16 (Chalcogens) because it has 6 valence electrons (4s² 4p⁴).
Belongs to Period 4 because its outermost electrons fill the n=4 shell.
Belongs to the p-block because its valence electrons occupy 4p orbitals.
Classified as a reactive nonmetal due to its covalent bonding chemistry and photoconductive nature.
Hover or tap any shell orbit ring to inspect electron counts and 2n² capacities.
Educational Note: This Niels Bohr planetary model visually illustrates principal quantum energy shells ($n=1, 2, 3\dots$) and electron counts. In modern quantum mechanics (Schrödinger model), electrons do not orbit in fixed circular planetary tracks, but exist as 3D probability clouds (orbitals: $s, p, d, f$) governed by the Heisenberg uncertainty principle.
Neutral ground state configuration. Valence electrons: 6.
Found as minor impurities in copper sulfide ores and elemental deposits around volcanic fumaroles.
From Greek 'Selene' meaning the Moon (analogous to Tellurium named after Earth)
Essential in trace amounts, but chronic overexposure causes selenosis, loss of hair/nails, and garlic breath odor.