#48 / 118
48Cd112.41
Transition Metalssolid at STPD-block

Cadmium

Group: 12•Period: 5•Standard Atomic Weight: 112.41 u
Open Full Periodic TableView Bohr Model

Why is Cadmium in this position?

Understanding the scientific rationale behind Cadmium's position in the periodic table:

Group Assignment
Group 12

Belongs to Group 12 because it has 2 valence electrons beyond a filled 4d¹⁰ subshell (4d¹⁰ 5s²).

Period Assignment
Period 5

Belongs to Period 5 because its outermost electrons occupy n=5.

Orbital Block
D-block

Belongs to the d-block as the 4d subshell completes at cadmium.

Chemical Category
Transition Metals

Classified as a transition metal / group 12 metal with exclusive +2 oxidation state.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 18, 2]

Bohr Atomic Shell Model(2, 8, 18, 18, 2)

Hover or tap any shell orbit ring to inspect electron counts and 2n² capacities.

48 Protons (p⁺)64 Neutrons (n⁰)
KShell K: Electron 1 of 2Shell K: Electron 2 of 2LShell L: Electron 1 of 8Shell L: Electron 2 of 8Shell L: Electron 3 of 8Shell L: Electron 4 of 8Shell L: Electron 5 of 8Shell L: Electron 6 of 8Shell L: Electron 7 of 8Shell L: Electron 8 of 8MShell M: Electron 1 of 18Shell M: Electron 2 of 18Shell M: Electron 3 of 18Shell M: Electron 4 of 18Shell M: Electron 5 of 18Shell M: Electron 6 of 18Shell M: Electron 7 of 18Shell M: Electron 8 of 18Shell M: Electron 9 of 18Shell M: Electron 10 of 18Shell M: Electron 11 of 18Shell M: Electron 12 of 18Shell M: Electron 13 of 18Shell M: Electron 14 of 18Shell M: Electron 15 of 18Shell M: Electron 16 of 18Shell M: Electron 17 of 18Shell M: Electron 18 of 18NShell N: Electron 1 of 18Shell N: Electron 2 of 18Shell N: Electron 3 of 18Shell N: Electron 4 of 18Shell N: Electron 5 of 18Shell N: Electron 6 of 18Shell N: Electron 7 of 18Shell N: Electron 8 of 18Shell N: Electron 9 of 18Shell N: Electron 10 of 18Shell N: Electron 11 of 18Shell N: Electron 12 of 18Shell N: Electron 13 of 18Shell N: Electron 14 of 18Shell N: Electron 15 of 18Shell N: Electron 16 of 18Shell N: Electron 17 of 18Shell N: Electron 18 of 18OShell O: Electron 1 of 2Shell O: Electron 2 of 2CdZ = 48

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.

Electron Shell Filling Breakdown

Shell K (n=1):2 / 2 electrons (100%)
Shell L (n=2):8 / 8 electrons (100%)
Shell M (n=3):18 / 18 electrons (100%)
Shell N (n=4):18 / 32 electrons (56%)
Shell O (n=5):2 / 50 electrons (4%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s²

Neutral ground state configuration. Valence electrons: 2.

Atomic & Quantum Properties

Electronegativity (Pauling)1.69 Pauling
1st Ionization Energy867.8 kJ/mol
Electron Affinity0 kJ/mol
Atomic Radius (empirical)161 pm
Common Oxidation States+2
Crystal StructureHCP

Physical & Thermal Properties

Density at STP8.65 g/cm³
Melting Point321.07 °C (594.22 K)
Boiling Point767 °C (1040 K)
Magnetic OrderingDiamagnetic
Discovery Year1817
Discovered ByKarl Samuel Leberecht Hermann & Friedrich Stromeyer

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Cadmium telluride (CdTe) thin-film photovoltaic solar panels
  • Corrosion-resistant sacrificial plating for military aircraft fasteners and bolts
  • Nuclear reactor control rods absorbing thermal neutrons
  • Brilliant artist pigments (Cadmium yellow / CdS, Cadmium red / CdSe)
Occurrence in Nature

Extracted exclusively as a byproduct of zinc ore smelting and refining (occurring in sphalerite ZnS).

Etymology & Name Origin

From Greek 'kadmeia', the ancient name for calamine (zinc carbonate ore)

Important Chemical Compounds
CdS (Cadmium sulfide / Cadmium yellow)
CdTe (Cadmium telluride)
CdO (Cadmium oxide)
Interesting Chemical Facts
  • • Cadmium was the cause of Itai-itai ('it hurts-it hurts') disease in Toyama Prefecture, Japan in 1912, where industrial runoff poisoned rice paddies causing brittle bone fractures.
  • • Cadmium telluride (CdTe) thin-film solar panels represent the second most common solar technology in the world after silicon.
  • • Cadmium has an extremely high thermal neutron capture cross section, making it an excellent emergency shutoff control rod in nuclear reactors.
Safety & Handling Note

Highly toxic cumulative poison that attacks the kidneys and softens bones; classified as a human carcinogen (IARC Group 1).

Explore Neighborhood Elements

Same Group (Group 12):
#30Zn#80Hg#112Cn
Same Period (Period 5):
#37Rb#38Sr#39Y#40Zr#41Nb#42Mo#43Tc#44Ru#45Rh#46Pd#47Ag#49In#50Sn#51Sb#52Te#53I#54Xe