Strontium Electron Configuration: [Kr] 5s² and Sr²⁺ Ion
The electron configuration of strontium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 which means that the first two electrons enter the 1s orbital. Since the 1s orbital can hold only two electrons, the next two will enter the 2s orbital. The next six electrons enter the 2p subshell. The p subshell can hold a maximum of six electrons. So first we put six electrons in the 2p subshell and then the next two electrons in the 3s orbital.
Since the 3s is now full, the electrons will move to the 3p subshell, where the next six electrons will enter. The 3p subshell is now full. Consequently, the following two electrons will enter the 4s orbital. Since the 4s orbital is full, the next ten electrons will move into the 3d subshell.
The 3d subshell is now full. Consequently, the next six electrons will enter the 4p subshell. Since the 4p is full, the remaining two electrons will move to the 5s orbital. Hence, the electron configuration of strontium will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2.
Strontium is the 38th element in the periodic table and the symbol is ‘Sr’. Strontium has an atomic number of 38, which means that its atom has 38 electrons around its nucleus. The electron configuration of strontium refers to the arrangement of electrons in the strontium atom’s orbitals. It describes how electrons are distributed among the various atomic orbitals and energy levels, and provides a detailed map of where each electron is likely to be found.
To understand the mechanism of strontium electron configuration, you must understand two basic things. These are orbits and orbitals. Also, you can arrange electrons in those two ways. In this article, I have discussed all the necessary points to understand the mechanism of strontium electron configuration, including noble gas notation, orbital diagram, valency, valence electrons, and the configuration for Sr²⁺ ion. I hope this will be helpful in your study.
Electron arrangement of Strontium through Bohr model
Scientist Niels Bohr was the first to give an idea of the atom’s orbit. He provided a model of the atom in 1913 and provided a complete idea of orbit in that model.
The electrons of the atom revolve around the nucleus in a certain circular path. These circular paths are called orbits (shells or energy levels). These orbits are expressed by n. [n = 1,2,3,4 . . . The serial number of the orbit]
The name of the first orbit is K, L is the second, M is the third, and N is the name of the fourth orbit. The electron holding capacity of each orbit is 2n2.
| Shell Number (n) | Shell Name | Electrons Holding Capacity (2n2) |
| 1 | K | 2 |
| 2 | L | 8 |
| 3 | M | 18 |
| 4 | N | 32 |
Explanation:
- Let, n = 1 for K orbit. So, the maximum electron holding capacity in the K orbit is 2n2 = 2 × 12 = 2 electrons.
- n = 2, for L orbit. The maximum electron holding capacity in the L orbit is 2n2 = 2 × 22 = 8 electrons.
- n=3 for M orbit. The maximum electron holding capacity in the M orbit is 2n2 = 2 × 32 = 18 electrons.
- n=4 for N orbit. The maximum electron holding capacity in N orbit is 2n2 = 2 × 42 = 32 electrons.
Therefore, the maximum electron holding capacity in the first shell is two, the second shell is eight and the 3rd shell can have a maximum of eighteen electrons.
The atomic number is the number of electrons in that element. The atomic number of strontium is 38. That is, the number of electrons in strontium is thirty-eight. Therefore, a strontium atom will have two electrons in the first shell, eight in the 2nd orbit, eighteen electrons in the 3rd shell, eight electrons in the 4th shell, and the remaining two electrons in the 5th shell. Therefore, the order of the number of electrons in each shell of the strontium atom is 2, 8, 18, 8, 2.
The Bohr atomic model has many limitations. In the Bohr atomic model, the electrons can only be arranged in different shells but the exact position, orbital shape, and spin of the electron cannot be determined.
Also, electrons can be arranged correctly from 1 to 18 elements. The electron arrangement of any element with atomic number greater than 18 cannot be accurately determined by the Bohr atomic model following the 2n2 formula. We can overcome all limitations of the Bohr model following the electron configuration through orbital.
Electron configuration of Strontium through Aufbau Model
Atomic energy shells are subdivided into sub-energy levels. These sub-energy levels are also called orbital. The most probable region of electron rotation around the nucleus is called the orbital.
The sub-energy levels depend on the azimuthal quantum number. It is expressed by ‘l’. The value of ‘l’ is from 0 to (n – 1). The sub-energy levels are known as s, p, d, and f.
| Orbit Number | Value of ‘l’ | Number of subshells | Number of orbitals | Subshell name | Electrons holding capacity | Electron configuration |
| 1 | 0 | 1 | 1 | 1s | 2 | 1s2 |
| 2 | 0 1 | 2 | 1 3 | 2s 2p | 2 6 | 2s2 2p6 |
| 3 | 0 1 2 | 3 | 1 3 5 | 3s 3p 3d | 2 6 10 | 3s2 3p6 3d10 |
| 4 | 0 1 2 3 | 4 | 1 3 5 7 | 4s 4p 4d 4f | 2 6 10 14 | 4s2 4p6 4d10 4f14 |
Explanation:
- If n = 1,
(n – 1) = (1–1) = 0
Therefore, the value of ‘l’ is 0. So, the sub-energy level is 1s. - If n = 2,
(n – 1) = (2–1) = 1.
Therefore, the value of ‘l’ is 0, 1. So, the sub-energy levels are 2s, and 2p. - If n = 3,
(n – 1) = (3–1) = 2.
Therefore, the value of ‘l’ is 0, 1, 2. So, the sub-energy levels are 3s, 3p, and 3d. - If n = 4,
(n – 1) = (4–1) = 3
Therefore, the value of ‘l’ is 0, 1, 2, 3. So, the sub-energy levels are 4s, 4p, 4d, and 4f. - If n = 5,
(n – 1) = (n – 5) = 4.
Therefore, l = 0,1,2,3,4. The number of sub-shells will be 5 but 4s, 4p, 4d, and 4f in these four subshells it is possible to arrange the electrons of all the elements of the periodic table.
| Sub-shell name | Name source | Value of ‘l’ | Value of ‘m’ (0 to ± l) | Number of orbital (2l+1) | Electrons holding capacity 2(2l+1) |
| s | Sharp | 0 | 0 | 1 | 2 |
| p | Principal | 1 | −1, 0, +1 | 3 | 6 |
| d | Diffuse | 2 | −2, −1, 0, +1, +2 | 5 | 10 |
| f | Fundamental | 3 | −3, −2, −1, 0, +1, +2, +3 | 7 | 14 |
The orbital number of the s-subshell is one, three in the p-subshell, five in the d-subshell, and seven in the f-subshell. Each orbital can have a maximum of two electrons.
The sub-energy level ‘s’ can hold a maximum of two electrons, ‘p’ can hold a maximum of six electrons, ‘d’ can hold a maximum of ten electrons, and ‘f’ can hold a maximum of fourteen electrons.
Aufbau is a German word, which means building up. The main proponents of this principle are scientists Niels Bohr and Pauli. The Aufbau method is to do electron configuration through the sub-energy level.
The Aufbau principle is that the electrons present in the atom will first complete the lowest energy orbital and then gradually continue to complete the higher energy orbital.
The energy of an orbital is calculated from the value of the principal quantum number ‘n’ and the azimuthal quantum number ‘l’. The orbital for which the value of (n + l) is lower is the low energy orbital and the electron will enter that orbital first.
| Orbital | Orbit (n) | Azimuthal quantum number (l) | Orbital energy (n + l) |
| 3d | 3 | 2 | 5 |
| 4s | 4 | 0 | 4 |
Here, the energy of 4s orbital is less than that of 3d. So, the electron will enter the 4s orbital first and enter the 3d orbital when the 4s orbital is full. Following the Aufbau principle, the sequence of entry of electrons into orbitals is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p.
Therefore, the complete electron configuration for strontium should be written as 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2.
Note: The unabbreviated electron configuration of strontium is [Kr] 5s2. When writing an electron configuration, you have to write serially.
Strontium ion(Sr2+) electron configuration
The ground state electron configuration of strontium is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s2. This electron configuration shows that the last shell of strontium has two electrons. Therefore, the valence electrons of strontium are two.
The elements that have 1, 2, or 3 electrons in the last shell donate the electrons in the last shell during bond formation. The elements that form bonds by donating electrons are called cations.
The strontium atom donates two electrons of the last shell to form bonds and turns into a strontium ion(Sr2+). That is, strontium is a cation element.
Sr – 2e– → Sr2+
The electron configuration of strontium ion(Sr2+) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6. This electron configuration of strontium ion shows that the strontium ion(Sr2+) has acquired the electron configuration of krypton and it achieves a stable electron configuration.
This post does a great job of breaking down the electron configuration of strontium and its ion! I appreciate the clarity in explaining how the transition from neutral strontium to Sr²⁺ occurs. It really helps in understanding the underlying concepts of electron behavior in different states. Looking forward to more posts like this!
This post really clarified my understanding of strontium’s electron configuration! It’s interesting how the transition to Sr²⁺ ion simplifies the configuration. The visual aids were particularly helpful. Thanks for breaking down such a complex topic!
Great explanation of strontium’s electron configuration! It’s fascinating how easily it transitions to Sr²⁺. I appreciate the clarity on how the filled inner shells of krypton play a role in its stability. Looking forward to more posts like this!
Great explanation of strontium’s electron configuration! I find it fascinating how the transition from neutral Sr to the Sr²⁺ ion involves losing those outer 5s electrons. It really highlights the delicate balance in electron behavior and stability. Thanks for breaking it down so clearly!
Great explanation of strontium’s electron configuration! I found it really helpful to see how it transitions to the Sr²⁺ ion. The comparison with krypton as a noble gas reference was particularly clear. Thanks for breaking it down so effectively!
This post really clarified the electron configuration for strontium and its ion! I appreciate how you explained the transition from [Kr] 5s² to Sr²⁺ ion. It makes the concept so much easier to understand. Thanks for sharing!
This post really helped clarify the electron configuration of strontium! I appreciate how you explained the transition from the neutral Sr atom to the Sr²⁺ ion. It’s fascinating to see how the electron loss affects its properties. Thanks for breaking it down so clearly!
Great explanation of strontium’s electron configuration! I appreciate the clarity in breaking down how the [Kr] 5s² configuration leads to the formation of the Sr²⁺ ion. It really helped me understand the concept better!
Great article! I found the explanation of strontium’s electron configuration really clear and helpful, especially how you broke down the [Kr] 5s² notation. Understanding the Sr²⁺ ion and its implications in various chemical contexts was also enlightening. Thanks for sharing!
Great explanation of strontium’s electron configuration! I found the comparison between the neutral atom and its Sr²⁺ ion very insightful. It really helped clarify how the removal of those two 5s electrons affects its stability and reactivity. Thanks for the informative post!
Great post! I found the explanation of strontium’s electron configuration really helpful, especially how it relates to the formation of the Sr²⁺ ion. It’s amazing how the noble gas notation simplifies understanding these concepts. Looking forward to more posts like this!
Great explanation of strontium’s electron configuration! I appreciate how you broke down the transition to the Sr²⁺ ion; it really clarified the concept for me.