Rhodium (Rh)
Element 45 · Transition metal · Solid at 25 °C · Group 9, Period 5
Rhodium is among the rarest and most expensive precious metals; most of it goes into catalytic converters that clean vehicle exhaust.
On the periodic table, rhodium sits in group 9 in period 5. It is one of 38 elements classified as a transition metal, and at room temperature (25 °C) it is a solid.
Transition metals occupy the wide d-block in the middle of the table. As a family they are hard, dense, high-melting metals that conduct heat and electricity well. Their partly filled d-orbitals let many of them take several oxidation states, form vividly colored compounds, and act as catalysts — which is why so much of industry, and so much of biology, runs on this block.
Properties of rhodium
| Atomic number (Z) | 45 |
|---|---|
| Symbol | Rh |
| Atomic mass | 102.91 |
| Category | Transition metal |
| Group | 9 |
| Period | 5 |
| Block | d-block |
| Metal / nonmetal | Metal |
| State at 25 °C | Solid |
| Electron configuration | [Kr] 4d8 5s1 |
| Electronegativity (Pauling) | 2.28 |
| Melting point | 1,964 °C (2,237.15 K / 3,567.2 °F) |
| Boiling point | 3,695 °C (3,968.15 K / 6,683 °F) |
| Density | 12.41 g/cm³ |
Position in the periodic table
Rhodium shares group 9 with Cobalt (Co), Iridium (Ir), Meitnerium (Mt). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.
Physical properties
Rhodium melts at 1,964 °C (2,237.15 K / 3,567.2 °F) and boils at 3,695 °C (3,968.15 K / 6,683 °F), giving it a liquid range of about 1,731 °C at standard pressure.
Its density is 12.41 g/cm³.
See also: the interactive periodic table, how to read the periodic table, periodic trends.