Understanding the scientific rationale behind Indium's position in the periodic table:
Belongs to Group 13 because it has 3 valence electrons (5s² 5p¹).
Belongs to Period 5 because its outermost occupied shell is n=5.
Belongs to the p-block because its differentiating electron enters a 5p orbital.
Classified as a post-transition metal with low melting point (156.6 °C) and high ductility.
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: 3.
Extremely scarce as independent minerals; recovered as a minor byproduct of sphalerite zinc sulfide ore refining.
From the brilliant indigo-blue line in its emission spectrum
Low toxicity in elemental metallic form, but indium tin oxide inhalation causes pulmonary alveolar proteinosis in electronics workers.