What Is Cadmium?
With atomic number 48 and chemical symbol Cd, Cadmium sits among the post-transition metals just right of the main transition block.
A soft bluish-white metal. Highly toxic. Used in rechargeable NiCd batteries.
As a post-transition metal in Period 5 and Group 12 (Transition Metals), cadmium's placement on the table reflects its electron configuration of [Kr] 4d¹⁰ 5s², which governs its bonding behavior and the type of compounds it typically forms.
Position on the Periodic Table
Cadmium is located in Period 5, which continues the transition metal pattern seen in Period 4 but one principal shell further out.
Within that row, cadmium sits in Group 12 (Transition Metals), alongside elements that share a similar number of valence electrons and, by extension, similar chemical behavior.
This position is not arbitrary — the periodic table was deliberately organized so that an element's row and column reveal its expected reactivity, bonding pattern, and physical state at a glance.
Physical & Chemical Properties
Cadmium has an atomic mass of 112.414 u and a density of 8.65 g/cm³. Its melting point is 321.1°C and its boiling point is 767°C.
Cadmium is generally softer and lower-melting than the transition metals positioned to its left on the periodic table.
Electron Configuration Explained
Cadmium's electron configuration is [Kr] 4d¹⁰ 5s², describing how its electrons are distributed across shells and subshells around the nucleus.
Reading the configuration in order shows electrons filling shells of increasing energy, following the standard Aufbau principle that explains how atomic structure builds up across the periodic table.
The outermost (valence) electrons shown in this configuration are what ultimately determine cadmium's chemical reactivity and the type of bonds it forms with other elements.
History & Discovery
Cadmium was formally discovered in 1817, Stromeyer, identified through the careful isolation and analytical techniques typical of that era's chemical research.
Many elements from this period were anticipated by Dmitri Mendeleev's periodic table, which successfully predicted gaps corresponding to undiscovered elements well before laboratory instruments existed to confirm them directly.
What Is Cadmium Used For?
Cadmium's specific properties make it useful in several applications, including:
- Ni-Cd batteries
- Nuclear control rods
- Pigments
- Electroplating
- Solar cells
These uses reflect cadmium's underlying classification as a post-transition metal, since the same properties that define its category in chemistry also determine where it becomes practically useful.
Fun Facts About Cadmium
- Itai-itai disease in Japan in the 1950s was caused by cadmium pollution from a mine.
- Cadmium is element number 48 on the periodic table, in Period 5 and Group 12.
- Its standard atomic mass is 112.414 u, calculated from the natural abundance of its isotopes.
Frequently Asked Questions
What is Cadmium's atomic number?
Cadmium has atomic number 48.
What is Cadmium's chemical symbol?
Cadmium's symbol is Cd.
What group and period is Cadmium in?
Cadmium is in Period 5, Group 12 (Transition Metals).
What is Cadmium's atomic mass?
Cadmium's standard atomic mass is 112.414 u.