Neptunium Properties (25 Facts You Should Know)

Np or neptunium is the fourth member of the actinide series having radioactive nature. Let us discuss some facts related to neptunium in this article.

Neptunium is a heavy metal in the actinide series. Due to its radioactive nature, it has isotopes with a short life. Neptunium is the first transuranic element in the periodic table. It can be synthesized by the nuclear irradiation of neptunium.

In this article we will learn some characteristics of neptunium in the periodic table like its symbol, atomic mass, melting point, etc.

1. Neptunium symbol

The atomic symbol for neptunium is “Np” which is the predominant letter of the English alphabet of the element.

Neptunium Symbol

2. Neptunium group in the periodic table

Neptunium does not have any particular group like other actinides. Due to actinide contraction, it is placed in between the 3rd en 4th group in the periodieke tabel. 5f orbital is mainly responsible for this contraction.

3. Neptunium period in the periodic table

Np is placed in the 7th period because last available principle quantum number for neptunium is 7. The period of the neptunium is judged by the number of electrons which is greater than 86.

4. Neptunium block in the periodic table

Neptunium belongs to the f-blok of the periodic table, as it has 5f orbital as the valence orbital.

5. Neptunium atomic number

The atomic number of neptunium is 93 which means it has 93 electrons in the different orbitals.

6. Neptunium atomic Weight

The mass of one atom of neptunium is 237 according to the 12C scale, which indicates neptunium is 237/12th times carbon.

7. Neptunium Electronegativity according to Pauling

The electronegativity is recorded at 1.36 for neptunium as per the Pauling scale, which indicates that it is most electropositive in nature.

8. Neptunium atomic Density

The atomic density of neptunium is found to be 20.2 g/cm3 which indicates that it belongs to a super heavy element.

9. Neptunium melting point

The melting point of neptunium is low 6440C or 914K, as lower energy is required to break weak crystals like orthorhombic.

10. Neptunium boiling point

Neptunium has a higher boiling point of 39020C to 4175K as it is a super heavy element and needs more energy to get boiled off from liquid to a gaseous state.

11. Neptunium Van der Waals radius

The van der Waal’s radius of neptunium is 200 pm because

  • neptunium has a 6s orbital which is subject to relativistic contraction
  • neptunium has 6d and 5f orbital which has a poor shielding effect and for this reason nucleus attracted the outermost electron towards itself and shortens the radius

12. Neptunium ionic radius

The ionic radius of neptunium is 200 pm because, in the ionic form, it can make a mono cation.

13. Neptunium isotopes

Elemente met dieselfde aantal elektrone maar verskillende massagetalle word genoem isotope of the original element. Let us discuss the isotopes of Neptunium.

Based on its radioactive nature and neutron numbers it has 29 isotopes –

  • 219Np
  • 220Np
  • 221Np
  • 222Np
  • 223Np
  • 224Np
  • 225Np
  • 226Np
  • 227Np
  • 228Np
  • 229Np
  • 230Np
  • 231Np
  • 232Np
  • 233Np
  • 234Np
  • 235Np
  • 236Np
  • 236mNp
  • 238Np
  • 238mNp
  • 239Np
  • 240Np
  • 240mNp
  • 241Np
  • 242Np
  • 243Np
  • 244Np

Only 4 isotopes of Neptunium are stable which are discussed below

Aantal van
235NpSintetiese396.1 dα, €142
236NpSintetiese1.5 * 105 yα, €, β143
237Npspoor2.14 * 106 yα144
238Uspoor2.35 dβ145
Isotopes of Neptunium


14. Neptunium electronic shell

The shell surrounding the nucleus as per principal quantum number and holding the electrons is called an electronic shell. Let us discuss the electronic shell of neptunium.

2 8 18 32 22 9 2 represents the correct electronic shell of neptunium as it has 93 electrons and to arrange those electrons in the set of orbitals we get this type of electronic shell around the nucleus in 1 to 7th orbitaal.

15. Neptunium electron configurations

1s2 2s2 2p6 3s2 3p3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f4 6s2 6p6 6d3 7s2 or [Rn]5f46d17s2 represent the electronic configuration of neptunium as per Hund’s rule. Here we arrange 93 electrons by the Aufbau principle in every orbital.

16. Neptunium energy of first ionization

Neptunium requires 604.5 KJ/mol  om remove the first electron from 7s and this is the value of the first ionization energy for the element.

17. Neptunium energy of second ionization

The energy required for the process is 1128KJ/mol as die 2nd electron is also removed from 7s orbital as it contains two electrons and because it is removed from the exciting system.

18. Neptunium energy of third ionization

The third I.E. for neptunium is 1997KJ/mol because it has the following reasons:

  • Neptunium has a 6s orbital and due to relativistic contraction, it has the strongest shielding effect so more energy will be required.
  • Along with 6s orbital, it has 5f and 6d orbital which have poor shielding effect so the nucleus attraction will be high
  • The third ionization occurs from the super exciting state of neptunium.

19. Neptunium oxidation states

Np has variable valency or oxidation state from +2 to +7, although it is an actinide. +5 oxidation state is more stable than any other oxidation state of Np.

20. Neptunium CAS number

The CAS number of the Neptunium molecule is 7439-99-8, wat deur die chemiese abstrakte diens gegee word.

21. Neptunium Chem Spider ID

The Chem Spider ID for Neptunium is 94588. By using this number, we can evaluate all the chemical data related to the Neptunium atom.

22. Neptunium allotropic forms

allotrope are elements or molecules with similar chemical properties but different physical properties. Let us discuss the allotropic form of neptunium.

Neptunium has three allotropic forms and they are –

  • α-Neptunium – which is orthorhombic in structure and stable at room temperature.
  • β-Neptunium – adopts a tetragonal lattice structure and exists at above 2800C.
  • γ-Neptunium – it has a cubic structure and is stable at above 5770C.

23. Neptunium chemical classification

The chemical classification of neptunium are –

  • Np is the rare earth element
  • Np is actinide heavy metal
  • Np is a weakly radioactive element
  • Np is transuranic element

24. Neptunium state at room temperature

Being a solid at room temperature Np adopts orthorhombic crystal in its lattice form.

25. Is Neptunium paramagnetic?

Paramagnetisme is the tendency of magnetization in the direction of the magnetic field. Let us see whether Neptunium is paramagnetic or not.

Neptunium shows paramagnetism as it has four unpaired electrons in valence 5f orbital and the value is not only dependent on the spin of electrons but there is some sort of orbital contribution as well.


Neptunium is a radioactive element so it can be used in nuclear reactors and making different or higher-order radioactive isotopes. It is a transuranic element so it has the same kind of properties as uranium and the +5 oxidation state is the most stable form of neptunium where it can form various organometallic clusters.

Biswarup Chandra Dey

Hi......ek is Biswarup Chandra Dey, ek het my Meestersgraad in Chemie voltooi. My spesialiseringsgebied is Anorganiese Chemie. Chemie gaan nie net oor lees reël vir reël en memorisering nie, dit is 'n konsep om op 'n maklike manier te verstaan ​​en hier deel ek met jou die konsep oor chemie wat ek leer omdat kennis die moeite werd is om dit te deel.

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