Promethium – Periodic Table (Element Information & More)

Promethium (Pm) element Periodic table

This is a SUPER easy guide on Promethium element.

In fact, the table mentioned below is the perfect information box (Which gives you every single detail about the Promethium element in Periodic table.)

So if you want to know anything about Promethium element, then this guide is for you.

Let’s finish this very quickly.

Promethium Element (Pm) Information

AppearanceMetallic appearance
State (at STP)Solid
Position in Periodic tablePromethium in periodic table (Position)
Group: lanthanides, Period: 6, Block: f
CategoryPromethium element category
Inner transition metals
Atomic number or 
Protons		61
Neutrons84
Electrons61
SymbolPm
Atomic mass Promethium (Pm) atomic mass
145 u
Electrons arrangement

or 

Bohr model		Bohr model of promethium (Electrons arrangement in promethium, Pm)
2, 8, 18, 23, 8, 2
Electronic configuration[Xe] 4f5 6s2
Atomic radiuspromethium (Pm) atomic radius
236 picometers (van der Waals radius)
1st Ionization energy5.55 eV
Crystal structurecrystal structure of promethium
Double hexagonal close packed
Melting point1315 K or 1042 °C or 1908 °F
Boiling point3273 K or 3000 °C or 5432 °F
Density7.26 g/cm3
Main isotope145Pm and 147Pm
Who discovered Promethium and when?Lawrence Glendenin, Jacob Marinsky, Charles Coryell (in 1945)
CAS number7440-12-2

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Promethium in Periodic table

Promethium element is in period 6 and in lanthanide group of the Periodic table. Promethium is the f-block element and it belongs to inner transition metals group.

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Why is Promethium in Period 6?

Why is Promethium in Period 6

Let me ask you a question.

How many shells does promethium have?

It’s 6. Right?

You have already seen the bohr model of promethium atom in the above table.

From the Bohr model, it can be found that the number of orbits or shells in promethium is 6. Hence, as promethium has 6 orbits, it lies in period 6 of the Periodic table. 

Why is Promethium in f-block?

Why is Promethium in f-block

Before knowing this reason, first of all I want to ask you a simple question.

How can you determine the blocks-wise position of elements?

The simple answer: The elements will lie in the s, p, d or f block will completely depend upon the subshell in which the last electron will enter.

For example; the electron configuration of promethium is [Xe] 6s2 4f5.

So the last electron of promethium enters the f-subshell or f-orbital. 

Hence, promethium is the f-block element.

5 Interesting facts about Promethium

Interesting facts about promethium element are mentioned below.

  1. Promethium is mostly found as a byproduct of the uranium fission reactions.
  2. Promethium was discovered by 3 chemists Lawrence Glendenin, Jacob Marinsky, Charles Coryell (in 1945).
  3. The existence of promethium was predicted by a chemist, Bohuslav Brauner in 1902.
  4. The name “promethium” was suggested by Charles Coryell’s wife (Grace Mary Coryell).
  5. Out of all the rare earth metals, the promethium was the last discovered rare earth metal.

Properties of Promethium

The physical and chemical properties of promethium element are mentioned below.

Physical properties of Promethium

Physical properties of promethium are mentioned below.

  • Promethium is silvery metallic in appearance and the salts of promethium glow with a greenish or bluish light in the dark.
  • The melting point of promethium is 1042 °C and its boiling point is 3000 °C.
  • The crystal structure of promethium is Double hexagonal close packed.
  • The atomic mass of the most stable isotope of promethium is 145 u and its density is 7.26 g/cm3.
  • Promethium has two naturally occurring isotopes, and they are 145Pm and 147Pm. Both of these isotopes are present in very trace amounts.

Chemical properties of Promethium

Chemical properties of promethium are mentioned below.

  • The isotopes of promethium are radioactive and it undergoes beta-decay.
  • The common oxidation state of promethium is +3, and this oxidation state is seen in most of the lanthanides.
  • The electron configuration of promethium is [Xe] 6s2 4f5 which indicates that the last electron enters the f-orbital. Because of this reason, it is a f-block element.
  • The first ionization energy of promethium is 5.55 eV.

Uses of Promethium

Uses of promethium are mentioned below.

  • Promethium is a very rare element and hence it does not have more uses. It is generally used for research work.
  • Promethium is used in nuclear batteries that are used in guided missiles as well as spacecraft.
  • There are possibilities that it can be used in medical devices.

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External resources:

  1. Promethium – Element information, properties and uses | Periodic Table. (n.d.). Promethium – Element Information, Properties and Uses | Periodic Table. https://www.rsc.org/periodic-table/element/61/promethium
  2. Promethium – Wikipedia. (2012, June 20). Promethium – Wikipedia. https://en.wikipedia.org/wiki/Promethium
  3. P. (n.d.). Promethium | Pm (Element) – PubChem. Promethium | Pm (Element) – PubChem. https://pubchem.ncbi.nlm.nih.gov/element/Promethium
  4. It’s Elemental – The Element Promethium. (n.d.). It’s Elemental – the Element Promethium. https://education.jlab.org/itselemental/ele061.html
  5. University of Sheffield and WebElements Ltd, M. W. (n.d.). WebElements Periodic Table » Promethium » the essentials. WebElements Periodic Table &Raquo; Promethium &Raquo; the Essentials. https://www.webelements.com/promethium/
  6. Periodic Table of Elements: Los Alamos National Laboratory. (n.d.). Periodic Table of Elements: Los Alamos National Laboratory. https://periodic.lanl.gov/61.shtml
  7. Periodic Table of Nottingham – University of Nottingham. (n.d.). Periodic Table of Nottingham – University of Nottingham. https://www.nottingham.ac.uk/periodicnottingham/promethium

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