What Is Rhodium?
Rhodium, symbol Rh and atomic number 45, belongs to the transition metals — the wide central block known for hardness and multiple oxidation states.
An extremely rare, hard, silvery-white metal. One of the most valuable metals on Earth.
As a transition metal in Period 5 and Group 9 (Transition Metals), rhodium's placement on the table reflects its electron configuration of [Kr] 4d⁸ 5s¹, which governs its bonding behavior and the type of compounds it typically forms.
Position on the Periodic Table
Rhodium is located in Period 5, which continues the transition metal pattern seen in Period 4 but one principal shell further out.
Within that row, rhodium sits in Group 9 (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
Rhodium has an atomic mass of 102.906 u and a density of 12.41 g/cm³. Its melting point is 1964°C and its boiling point is 3695°C.
Rhodium is malleable and ductile in its pure metallic form, and like other transition metals it can typically form more than one stable oxidation state.
Electron Configuration Explained
Rhodium's electron configuration is [Kr] 4d⁸ 5s¹, 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 rhodium's chemical reactivity and the type of bonds it forms with other elements.
History & Discovery
Rhodium was formally discovered in 1803, W.H. Wollaston, 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 Rhodium Used For?
Rhodium's specific properties make it useful in several applications, including:
- Catalytic converters
- Jewelry plating
- Electrical contacts
- Optical instruments
- Chemical catalysts
These uses reflect rhodium's underlying classification as a transition metal, since the same properties that define its category in chemistry also determine where it becomes practically useful.
Fun Facts About Rhodium
- Rhodium is the rarest non-radioactive metal on Earth — worth more than $10,000 per troy ounce.
- Rhodium is element number 45 on the periodic table, in Period 5 and Group 9.
- Its standard atomic mass is 102.906 u, calculated from the natural abundance of its isotopes.
Frequently Asked Questions
What is Rhodium's atomic number?
Rhodium has atomic number 45.
What is Rhodium's chemical symbol?
Rhodium's symbol is Rh.
What group and period is Rhodium in?
Rhodium is in Period 5, Group 9 (Transition Metals).
What is Rhodium's atomic mass?
Rhodium's standard atomic mass is 102.906 u.