Tl - Thallium

Thallium is used to form low-melting-point glass. It was once used as rat poison, but it is now banned from household use.

The table below shows the abundance of Thallium in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.

The solid state structure of Thallium is Simple Hexagonal.

The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.

Unit Cell Parameters

The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)

and the angles between them Lattice Angles (alpha, beta and gamma).

The positions of the atoms inside the unit cell are described by the set of atomic positions ( x_i, y_i, z_i) measured from a reference lattice point.

The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.

Space Group Name	P63/mmc
Space Group Number	194
Crystal Structure	Simple Hexagonal
Number of atoms per unit cell

Thallium atoms have 81 electrons and the electronic shell structure is [2, 8, 18, 32, 18, 3] with Atomic Term Symbol (Quantum Numbers) ²P_1/2.

Atomic Number	81
Number of Electrons (with no charge)	81
Number of Protons	81
Mass Number	204
Number of Neutrons	123
Shell structure (Electrons per energy level)	2, 8, 18, 32, 18, 3
Electron Configuration	[Xe] 4f14 5d10 6s2 6p1
Valence Electrons	6s2 6p1
Valence (Valency)	3
Main Oxidation States	1, 3
Oxidation States	-5, -2, -1, 1, 2, 3
Atomic Term Symbol (Quantum Numbers)	2P1/2

Bohr Atomic Model of Thallium - Electrons per energy level

n		s	p	d	f

Ground State Electronic Configuration of Thallium - neutral Thallium atom

Abbreviated electronic configuration of Thallium

The ground state abbreviated electronic configuration of Neutral Thallium atom is [Xe] 4f14 5d10 6s2 6p1. The portion of Thallium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Xe]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 6s2 6p1, electrons in the outermost shell that determine the chemical properties of the element.

Unabbreviated electronic configuration of neutral Thallium

Complete ground state electronic configuration for the Thallium atom, Unabbreviated electronic configuration

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p1

Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.

As per the Aufbau principle the electrons will occupy the orbitals having lower energies before occupying higher energy orbitals. According to this principle, electrons are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…

The Pauli exclusion principle states that a maximum of two electrons, each having opposite spins, can fit in an orbital.

Hund's rule states that every orbital in a given subshell is singly occupied by electrons before a second electron is filled in an orbital.

Atomic Structure of Thallium

Thallium atomic radius is 156 pm, while it's covalent radius is 148 pm.

Spectral Lines of Thallium - Atomic Spectrum of Thallium

A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules.

Spectral lines are the result of interaction between a quantum system and a single photon. A spectral line may be observed either as an emission line or an absorption line.

Spectral lines are highly atom-specific, and can be used to identify the chemical composition of any medium. Several elements, including helium, thallium, and caesium, were discovered by spectroscopic means. They are widely used to determine the physical conditions of stars and other celestial bodies that cannot be analyzed by other means.

Emission spectrum of Thallium

Absorption spectrum of Thallium

The electron affinity of Thallium is 19.2 kJ/mol.

Ionization Energy of Thallium

Ionization energy is the amount of energy required to remove an electron from an atom or molecule.in chemistry, this energy is expresed in kilocalories per mole (kcal/mol) or kilojoules per mole (kJ/mol).

Refer to table below for Ionization energies of Thallium

Refer to below table for Thallium Physical Properties

Elastic Properties

Hardness of Thallium - Tests to Measure of Hardness of Element

Thallium Electrical Properties

Electrical resistivity measures element's electrical resistance or how strongly it resists electric current.The SI unit of electrical resistivity is the ohm-metre (Ω⋅m). While Electrical conductivity is the reciprocal of electrical resistivity. It represents a element's ability to conduct electric current. The SI unit of electrical conductivity is siemens per metre (S/m).

Thallium is a conductor of electricity. Refer to table below for the Electrical properties of Thallium

Thallium Heat and Conduction Properties

Thallium Magnetic Properties

Optical Properties of Thallium

Acoustic Properties of Thallium

Refer to table below for Thermal properties of Thallium

Enthalpies of Thallium

Thallium has 37 isotopes, with between 176 and 212 nucleons. Thallium has 2 stable naturally occuring isotopes.

Isotopes of Thallium - Naturally occurring stable Isotopes: 203Tl, 205Tl.

The United States Department of Transportation (DOT) identifies hazard class of all dangerous elements/goods/commodities either by its class (or division) number or name. The DOT has divided these materials into nine different categories, known as Hazard Classes.

NFPA 704 is a Standard System for the Identification of the Hazards of Materials for Emergency Response. NFPA is a standard maintained by the US based National Fire Protection Association.

The health (blue), flammability (red), and reactivity (yellow) rating all use a numbering scale ranging from 0 to 4. A value of zero means that the element poses no hazard; a rating of four indicates extreme danger.

List of unique identifiers to search the element in various chemical registry databases