Thallium ( TI )

Define: Thallium is semi metal.  It is also called post transition metal . Just place after transition metal series. It is place  in below indium .it is very toxic and carcinogenic . It is found in earth crust in the form of pyrites ores. It is also found by the process of zinc, copper and cobalt refining

Discovery : it is discovered in 1861 by scientist William crookers .

Origin of name :the ne thallium is derived from the Greek word ‘ Thallos ‘ Meaning of this word is a green twig.

Physical properties :

Atomic symbol: Atomic symbol of Thallium is TI

Atomic number : atomic number of Thallium is 81

In thallium 81 proton and 81 Electron is present

Atomic weight/ mass: Atomic weight of Thallium is 204.38

In Thallium 81 proton and 123 neutron is present

Position : it is place in periodic table at 6th period ( row ) and 13 thcolumn ( group)

Block : it is place in p block

Colour : Thallium show grey

Nature : Thallium present in solid form in nature

Boiling point : boiling point of Thallium is 1473 0C

Melting point :melting point of Thallium is 304 0C

Isotopes: Thallium show 2 stable isotopes

  • 203 TI: atomic weight of this isotope is 202.9 Amu

In this isotope 81 proton,81 Electron and 122 neutron is present

It is present 29.5% in nature

  • 204TI: atomic weight of this isotope is 204.3 Amu

In this isotope 81 proton, 81 Electron and 123 neutron is present

It is present 70.48% in nature

Chemical Properties :

Electronic configuration

Electronic configuration of Thallium is [ Xe] 4f14 5d10 6s2 6p1

Electronic configuration in concert of shell is 2,8,18,32,18 ,3

Electronic structure

Valency : Valency of Thallium is 3,2 or 1

Atomic radius : Atomic radius of Thallium is 156 Pm


  • Oxide form use to make special glass.
  • It is use. In photocell
  • Thallium used in production of photocell
  • It is toxic and use in rodent killer
  • At the low temperature Thallium with mercury use in thermometer and switch
  • Mostly Thallium is used in electronic industry to make photoelectric cell.


Question and Answer:

Q1. Define Thallium

Q2. Who discovered Thallium?

Q2. Physical properties of Thallium

Q4. Write Atomic Symbol of Thallium.

Q5. Write the Atomic number of Thallium.

Q6. On which block Thallium element is present?

Q7. What is the color of Thallium?

Q8. What is the Boiling point of Thallium?

Q9. What is the Melting point of Thallium?

Q10. Write the Isotopes of Thallium.

Q11. Show Electronic configuration of Thallium.

Q12. Write Electronic Structure of Thallium.

Q13. What is the Valency of Thallium?

Q14. Write the uses of Thallium element.

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