Thallium (Tl) – Periodic Table [Element Information & More]

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.

Facts about thallium

Here are a few interesting facts about thallium.

1. William Crookes discovered thallium in the year 1861.
2. Thallium was given its name from the Greek word “thallos”, meaning green shoot.
3. The earth’s crust contains around 850 parts per billion (by weight) of thallium.
4. Around 70% of the total thallium is used in the electronics industries.
5. 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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