Yes. Thallium is a metal, classified as a post-transition metal on the periodic table.

How many protons does thallium have?

Thallium has 81 protons. Its atomic number is 81, which is also the number of electrons in a neutral atom of thallium.

What group and period is thallium in?

Thallium is in group 13 and period 6 of the periodic table, in the p-block.

What is the atomic mass of thallium?

The atomic mass of thallium is 204.38 u (unified atomic mass units).

Element 81

Thallium (Tl)

Post-transition metal · Period 6 · Group 13 · p-block

Thallium (Tl) is element 81 of the periodic table, a post-transition metal in period 6, group 13 (p-block) with an atomic mass of 204.38 and is a solid at standard conditions.

At a glance

Atomic number: 81
Symbol: Tl
Atomic mass: 204.38 u
Category: Post-transition metals
Period: 6
Group: 13
Block: p-block
Phase at STP: solid

Electron structure

Electron configuration: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p1
Shorthand configuration: [Xe] 4f14 5d10 6s2 6p1
Electrons per shell: 2, 8, 18, 32, 18, 3
Oxidation states: -5, -2, -1, +1, +3

Physical properties

Melting point: 577 K (303.85 °C)
Boiling point: 1,746 K (1,472.85 °C)
Density: 11.85 g/cm³
Phase: solid

Atomic properties

Electronegativity (Pauling): 1.62
Atomic radius: 156 pm
Covalent radius: 145 pm
Van der Waals radius: 196 pm
First ionization energy: 589 kJ/mol
Electron affinity: 19 kJ/mol

Notable isotopes

Notable isotopes of Thallium: mass number, atomic mass, natural abundance, and stability.
Isotope	Mass	Abundance	Stability
Tl-205	204.97441	70.48%	Stable

Common uses

Electronics
Medical imaging
Low-temperature thermometers
Infrared detectors

Discovery

Year: 1861
Discovered by: William Crookes
Country: England

Frequently asked questions

Is thallium a metal?: Yes. Thallium is a metal, classified as a post-transition metal on the periodic table.
How many protons does thallium have?: Thallium has 81 protons. Its atomic number is 81, which is also the number of electrons in a neutral atom of thallium.
What group and period is thallium in?: Thallium is in group 13 and period 6 of the periodic table, in the p-block.
What is the atomic mass of thallium?: The atomic mass of thallium is 204.38 u (unified atomic mass units).

Keep exploring

Thallium's row is on the printable element property sheet, and its tile is on the periodic table wall chart - the same numbers as above, laid out for A4 or A3 paper.