Cm or curium is the transuranic radioactive actinide metal element. Let us discuss curium in this article.
Curium is the 8th member of the actinide series. It is coming after uranium so it has radioactive properties. It appears a hard, dense, silvery metal. At the ambient condition, it shows paramagnetism whereas at lower temperatures it becomes antiferromagnetic.
In the following part, we should discuss the basic physical property of curium like melting point, ionization energy, allotropes, isotopes, etc.
1. Curium symbol
“Cm” is the abbreviation for the symbol of curium from the English alphabet, instead of C or Cu as starting letters are taken for carbon or copper elements.
2. Curium group in the periodic table
The group of curium in the periodic table is between the 3rd and 4th, as it is an actinide and the period of actinide is unpredictable due to actinide contraction of the 5f orbital.
3. Curium period in the periodic table
Like other actinides Cm belongs to the 7th period in the periodic table.
4. Curium block in the periodic table
Due to the presence of valence 5f orbital curium is an f-block element, although it has s, p, and d orbital due to the Aufbau principle the last orbital is 5f.
5. Curium atomic number
The z value of curium is 96 which is its atomic number, so it has 96 electrons and protons. Both have the same numbers and opposite charges to maintain electrical neutrality.
6. Curium atomic Weight
As per the 12C scale, the atomic weight of curium is 247 which means it is 247/12th of the weight of the atomic weight of carbon itself.
7. Curium Electronegativity according to Pauling
According to the Pauling scale, the electronegativity of Curium is 1.3 which indicates it is more electropositive as it is rare earth metal, which possesses an electropositive character.
8. Curium atomic Density
The atomic density of Curium is very high which is 20.2 g/cm3 as it is a super heavy element.
Density is calculated by the formula, atomic density = atomic mass / atomic volume.
9. Curium melting point
The energy required to melt the crystal of curium is 13470C or 1620K which is its melting point, as it adopts double hexagonal close-packed so required more energy to break the crystal.
10. Curium boiling point
31100C to 3383K is the boiling temperature or boiling point of curium, as it is radioactive in nature so it required more energy than its melting point to get boiled off from the liquid state.
11. Curium Van der Waals radius
Like another transuranic actinide, van der Waal’s radius of curium is 200 pm. Because it has a 7s orbital which has greater spatial distribution so the value will be high but due to the poor screening effect of 5f and 6d orbitals nuclear attraction on the outer orbital increases and the radius will be decreased.
12. Curium ionic radius
The ionic radius is the same as van der Waal’s radius of curium is 200 pm. As it forms the same ionic value as the curium.
13. Curium isotopes
Elements having the same number of electrons but different mass numbers are called isotopes of the original element. Let us discuss the isotopes of Curium.
On the basis of neutrons, number neptunium has 28 isotopes –
- 233Cm
- 234Cm
- 235Cm
- 236Cm
- 237Cm
- 238Cm
- 239Cm
- 240Cm
- 241Cm
- 242Cm
- 242mCm
- 233Cm
- 243Cm
- 243mCm
- 244Cm
- 244m1Cm
- 244m2Cm
- 245Cm
- 245mCm
- 246Cm
- 246mCm
- 247Cm
- 247m1Cm
- 247m2Cm
- 248Cm
- 248mCm
- 249Cm
- 249mCm
- 250Cm
- 251Cm
Here only stable isotopes are discussed below –
| Isotope | Natural Abundance | Half-life | Emitting particles | No. of Neutron |
| 242Cm | Synthetic | 160 d | α, SF | 146 |
| 243Cm | Synthetic | 29.1 y | α, €, SF | 147 |
| 24Cm | Synthetic | 18.1 y | α, SF | 148 |
| 245Cm | Synthetic | 8500 y | α, SF | 149 |
| 246Cm | Synthetic | 4730 y | α, SF | 150 |
| 247Cm | Synthetic | 1.56 *107 y | α | 151 |
| 248Cm | Synthetic | 3.40 *105 y | α, SF | 152 |
| 250Cm | Synthetic | 9000 y | α, β, SF | 154 |
14. Curium 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 Curium.
2 8 18 32 25 9 2 is the set of the electronic shell of curium as it contains 96 electrons and those electrons can be arranged around the nucleus in the s, p, d, and f orbital in this way by their principle as well as magnetic quantum number.
15. Curium electron configurations
According to Hund’s rule the correct electronic configuration of Curium [Rn]5f76d17s2 or 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f7 6s2 6p6 6d1 7s2 because it is consist of 96 electrons, those electrons are placed at s, p, d, and f orbitals of respective principle quantum number.
16. Curium energy of first ionization
The energy required for the removal of the first electron for curium is 581 KJ/mol which occurs from 7s orbital and due to relativistic contraction the energy will be high for the first I.E.
17. Curium energy of second ionization
1196 KJ/mol is the second ionization energy required for of curium. The 2nd electron is removed from the 7s orbital of curium which is already in +1 excited state and for this reason, the 2nd ionization is reasonably high than the previous one, although there is no stabilizing factor present.
18. Curium energy of third ionization
The third ionization energy for Curium is 1997 KJ/mol and the reasons are –
- The third electron is removed from 6d instead of 5f due to exchange energy
- 6d shields the nucleus very poorly and for this reason, nuclear attraction force will be high
- Third ionization occurs from the +2 excited state of a system.
19. Curium oxidation states
Like other actinides, Cm shows a +3 oxidation state and besides this, it shows +4, +5, and +6 oxidation states which are also stable due to the availability of electrons in its valence and pre-ultimate orbitals.
20. Curium CAS number
As per the chemical abstracts service, The CAS number of the Curium molecule is 7440-51-9.
21. Curium Chem Spider ID
22415 is the chem spider id for the curium.
22. Curium allotropic forms
Allotropes are elements or molecules with similar chemical properties but different physical properties. Let us discuss the allotropic form of curium.
Due to its highly radioactive nature, there is no allotropic form of curium is found.
23. Curium chemical classification
Curium can be classified into the following classes –
- Curium is one of transuranic element
- Curium is the strongest radioactive metal
- Curium is also rare earth metal like another actinide
24. Curium state at room temperature
Due to the double hexagonal close-packed lattice solid form is the best for curium at room temperature of in the crystal.
25. Is Curium paramagnetic?
Paramagnetism is the tendency of magnetization in the direction of the magnetic field. Let us see whether curium is paramagnetic or not.
Curium is paramagnetic in nature due to the presence maximum number that is 7 unpaired electrons present in the 5f orbital but being a strong radioactive element we cannot predict the magnetic molar susceptibility.
Conclusion
Like other actinides, curium is a radioactive element and it can form strongly fluorescent organometallics complexes with different ligands.
Hi……I am Biswarup Chandra Dey, I have completed my Master’s in Chemistry from the Central University of Punjab. My area of specialization is Inorganic Chemistry. Chemistry is not all about reading line by line and memorizing, it is a concept to understand in an easy way and here I am sharing with you the concept about chemistry which I learn because knowledge is worth to share it.