
Thallium element (Tl) is in group 13 and period 6 of a periodic table. Thallium is in the p-block and it is classified as a post-transition element on the periodic table.
There is a lot more information related to thallium which is mentioned in the Information Table given below.
So let’s dive right into it!
Table of contents
- Thallium element (Information Table)
- Thallium element in Periodic table
- Facts about Thallium
- Properties of Thallium
- Uses of Thallium
Thallium Element (Information Table)
The important data related to thallium element is given in the table below.
Appearance of thallium | Silvery gray appearance |
Atomic number of thallium | 81 |
Symbol of thallium | Tl |
Atomic mass of thallium | 204.38 u |
Protons, Neutrons & Electrons in thallium | Protons: 81, Neutrons: 123, Electrons: 81 |
State of thallium (at STP) | Solid |
Group number of thallium in periodic table | 13 |
Period number of thallium in periodic table | 6 |
Block of thallium in periodic table | p-block |
Category of thallium | Post transition element (boron group) |
Bohr model or Electrons per shell or Electrons arrangement in thallium | 2, 8, 18, 32, 18, 3 |
Electron configuration of thallium | [Xe] 4f14 5d10 6s2 6p1 |
Orbital diagram of thallium | ![]() |
Valence electrons in thallium | 3 |
Electronegativity of thallium (on pauling scale) | 1.62 |
Atomic radius of thallium (van der Waals radius) | 196 picometers |
Density of thallium | 11.85 g/cm3 |
1st ionization energy of thallium | 6.108 eV |
Main isotope of thallium | 205Tl |
Melting point of thallium | 577 K or 304 °C or 579 °F |
Boiling point of thallium | 1746 K or 1473 °C or 2683 °F |
Crystal structure of thallium | Hexagonal Close Packed (HCP) |
Discovery of thallium | By William Crookes (in 1861) |
Also see: Interactive Periodic Table (It has rotating bohr models as well as many other details of all the 118 elements in a single periodic table).
Thallium element in Periodic table
The Thallium element (Tl) has the atomic number 81 and is located in group 13 and period 6. Thallium is a metal and it is classified as a post-transition element.
H | He | ||||||||||||||||
Li | Be | B | C | N | O | F | Ne | ||||||||||
Na | Mg | Al | Si | P | S | Cl | Ar | ||||||||||
K | Ca | Sc | Ti | V | Cr | Mn | Fe | Co | Ni | Cu | Zn | Ga | Ge | As | Se | Br | Kr |
Rb | Sr | Y | Zr | Nb | Mo | Tc | Ru | Rh | Pd | Ag | Cd | In | Sn | Sb | Te | I | Xe |
Cs | Ba | La* | Hf | Ta | W | Re | Os | Ir | Pt | Au | Hg | Tl | Pb | Bi | Po | At | Rn |
Fr | Ra | Ac** | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og |
*Ce | Pr | Nd | Pm | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu | ||||
**Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr |
Facts about thallium
Here are a few interesting facts about thallium.
- William Crookes discovered thallium in the year 1861.
- Thallium was given its name from the Greek word “thallos”, meaning green shoot.
- The earth’s crust contains around 850 parts per billion (by weight) of thallium.
- Around 70% of the total thallium is used in the electronics industries.
- Thallium is stored in mineral oil because of its reactivity.
Properties of thallium
Here is a list of some physical properties and chemical properties of thallium.
Physical properties of thallium
- Thallium has a silvery gray appearance.
- Thallium is soft metal and it can be cut with a knife too.
- The density of thallium is 11.85 g/cm3 and its atomic mass is 204.38 amu.
- The melting point and boiling point of thallium is 577 K and 1746 K respectively.
- Thallium has HCP crystal structure.
- Thallium has many isotopes, and the most abundant isotope is 205Tl.
Chemical properties of thallium
- Thallium easily reacts with the atmospheric oxygen and tarnishes, if kept open in the air.
- Thallium reacts with water and forms a thallium hydroxide.
- Thallium has an electronegativity of 1.62 on the pauling scale.
Uses of thallium
Here are some uses of the thallium element.
- Thallium oxide is used in making glasses that require a higher refractive index.
- Thallium is also used in electronic industries (specially in the semiconductor material used for selenium rectifiers).
- Thallium sulfide is a compound of thallium which is used in photocells.
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