Terbium (Tb)

Terbium properties

Atomic number

65

Atomic mass

158.93 u

Category

Lanthanide

Group

—

Period

6

Block

f-block

State at room temp.

Solid

Electronegativity

1.2

Melting point

1,629 K (1,355.8 °C)

Boiling point

3,503 K (3,229.8 °C)

Density

8.23 g/cm³

Valence electrons

2

Common charges

+3

Oxidation states

+3

Atomic radius

221 pm

Ionization energy

5.864 eV

Electron affinity

—

Radioactive

No, has stable isotopes

Discovered

1843

Terbium electron configuration

The electron configuration of Terbium (Tb) is [Xe] 4f9 6s2. Its 65 electrons are arranged in shells as 2, 8, 18, 27, 8, 2.

Protons, neutrons and electrons in Terbium

A neutral Terbium atom has 65 protons and 65 electrons. Most Terbium atoms have about 94 neutrons: the atomic mass rounded to 159, minus the atomic number 65.

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

How many valence electrons does Terbium have?

2

Terbium has 2 valence electrons in its outermost shell. As an f-block element, its 4f or 5f electrons can also take part in bonding.

See every element: Periodic table with valence electrons

Terbium 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 Terbium

158.93 g/mol

One mole of Terbium atoms (6.022 × 10²³ atoms) has a mass of 158.93 grams. Use this value to convert between grams and moles.

Terbium facts

• Terbium is one of four elements named after the Swedish village of Ytterby, along with yttrium, erbium, and ytterbium.
• The names terbium and erbium were swapped between the 1860s and 1870s, so Mosander's original 'terbia' is today's erbium oxide.
• Terbium (Tb) has atomic number 65 and is a solid at room temperature. It was discovered in 1843.

Position in the periodic table

Terbium is element 65, in period 6 of the periodic table. It is one of the Lanthanides in the f-block, shown in the rows below the main table.

All lanthanides

Uses of Terbium

Terbium is used in green phosphors for fluorescent lamps and some display screens. It is a key part of Terfenol-D, an alloy that changes shape in a magnetic field and is used in sonar systems, sensors, and precise actuators. Small amounts of terbium are added to neodymium magnets to help them stay strong at the high temperatures inside electric motors.

Who discovered Terbium?

Swedish chemist Carl Gustaf Mosander discovered terbium in 1843 in Stockholm, when he separated yttria, an oxide from the mineral gadolinite, into three fractions.

Where does the name come from?

Terbium is named after Ytterby, a village near Stockholm in Sweden whose quarry produced the mineral it came from. Carl Gustaf Mosander discovered it in 1843 and built its name from part of the village's name.

Discovery timeline