Rhodium (Rh)

Rhodium properties

Atomic number

45

Atomic mass

102.91 u

Category

Transition metal

Group

9

Period

5

Block

d-block

State at room temp.

Solid

Electronegativity

2.28

Melting point

2,237 K (1,963.8 °C)

Boiling point

3,968 K (3,694.8 °C)

Density

12.41 g/cm³

Valence electrons

1

Common charges

+3

Oxidation states

+3

Atomic radius

195 pm

Ionization energy

7.459 eV

Electron affinity

1.137 eV

Radioactive

No, has stable isotopes

Discovered

1804

Rhodium electron configuration

The electron configuration of Rhodium (Rh) is [Kr] 4d8 5s1. Its 45 electrons are arranged in shells as 2, 8, 18, 16, 1.

Protons, neutrons and electrons in Rhodium

A neutral Rhodium atom has 45 protons and 45 electrons. Most Rhodium atoms have about 58 neutrons: the atomic mass rounded to 103, minus the atomic number 45.

Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass

How many valence electrons does Rhodium have?

1

Rhodium has 1 valence electron, counting the electrons in its outermost s subshell. Like most transition metals, it can also use d electrons in bonding.

See every element: Periodic table with valence electrons

Rhodium orbital diagram

Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations

Molar mass of Rhodium

102.91 g/mol

One mole of Rhodium atoms (6.022 × 10²³ atoms) has a mass of 102.91 grams. Use this value to convert between grams and moles.

Rhodium facts

• Rhodium's name comes from the Greek rhodon, meaning 'rose', because many of its salts are rose-red.
• In 1979 the Guinness Book of Records gave Paul McCartney a rhodium-plated disc for being the best-selling songwriter and recording artist of all time.
• Rhodium (Rh) has atomic number 45 and is a solid at room temperature. It was discovered in 1804.

Position in the periodic table

Rhodium is element 45, in period 5 and group 9 of the periodic table, in the d-block.

All transition metals

Uses of Rhodium

Rhodium's most important use is in catalytic converters, where it helps turn harmful nitrogen oxides in car exhaust into harmless nitrogen. It is also plated onto white gold and silver jewelry to give a bright, hard, tarnish-resistant finish. Platinum–rhodium alloys are used in thermocouples that measure very high temperatures and in the equipment used to make glass fibers.

Who discovered Rhodium?

English chemist William Hyde Wollaston discovered rhodium in London shortly after palladium and announced it in 1804. He found it after dissolving South American platinum ore in aqua regia and removing the platinum and palladium.

Where does the name come from?

Rhodium comes from the Greek rhodon, meaning 'rose'. William Hyde Wollaston chose the name in the early 1800s because the salts of the new metal he isolated had a rosy red color.

Discovery timeline