Strontium(Sr) electron configuration and orbital diagram

Strontium(Sr) is the 38th element in the periodic table and its symbol is ‘Sr’. The electron configuration of strontium and the orbital diagram is the main topic in this article. Also, valency and valence electrons of strontium, compound formation, bond formation have been discussed. Hopefully, after reading this article you will know in detail about this.

The total number of electrons in strontium is thirty-eight. These electrons are arranged according to specific rules of different orbits. The arrangement of electrons in different orbits and orbitals of an atom in a certain order is called electron configuration. The electron configuration of strontium(Sr) atoms can be done in two ways.

Electron configuration through orbit
Electron configuration through orbital

Electron configuration through orbitals follows different principles. For example Aufbau principle, Hund’s principle, Pauli’s exclusion principle. There is an article published on this site detailing the electron configuration, you can read it if you want.

Table of Contents

Strontium(Sr) electron configuration through orbit

Scientist Niels Bohr was the first to give an idea of the atom’s orbit. He provided a model of the atom in 1913. The complete idea of the orbit is given there. The electrons of the atom revolve around the nucleus in a certain circular path. These circular paths are called orbit(shell). These orbits are expressed by n. [n = 1,2,3,4 . . . The serial number of the orbit]

Strontium (Sr) atom electron configuration (Bohr model)

K is the name of the first orbit, L is the second, M is the third, N is the name of the fourth orbit. The electron holding capacity of each orbit is 2n².

For example,

n = 1 for K orbit.
The electron holding capacity of K orbit is 2n² = 2 × 1² = 2 electrons.
For L orbit, n = 2.
The electron holding capacity of the L orbit is 2n² = 2 × 2² = 8 electrons.
n=3 for M orbit.
The maximum electron holding capacity in 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(Sr) 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 will be 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.

Electrons can be arranged correctly through orbits from elements 1 to 18. The electron configuration of an element with an atomic number greater than 18 cannot be properly determined according to the Bohr atomic model. The electron configuration of all the elements can be done through the orbital diagram.

Electron configuration of strontium(Sr) through orbital

The German physicist Aufbau first proposed an idea of electron configuration through sub-orbits. The Aufbau method is to do electron configuration through the sub-energy level. These sub-orbitals are expressed by ‘l’. 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. These orbitals are named s, p, d, f. The electron holding capacity of these orbitals is s = 2, p = 6, d = 10 and f = 14. The Aufbau electron configuration method is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d.

Electron configuration via Aufbau principal

The first two electrons of strontium enter the 1s orbital. The s-orbital can have a maximum of two electrons. Therefore, the next two electrons enter the 2s orbital. The p-orbital can have a maximum of six electrons. So, the next six electrons enter the 2p orbital. The second orbit is now full. So, the remaining electrons will enter the third orbit. Then two electrons will enter the 3s orbital and the next six electrons will be in the 3p orbital of the third orbit. The 3p orbital is now full. So, the next two electrons will enter the 4s orbital and ten electrons will enter the 3d orbital. The 3d orbital is now full. So, the next six electrons enter the 4p orbital. The 4p orbital is now full. Then the remaining two electrons will enter the 5s orbital. Therefore, the strontium(Sr) electron configuration will be 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s².

How to write the orbital diagram for strontium(Sr)?

To create an orbital diagram of an atom, you first need to know Hund’s principle and Pauli’s exclusion principle. Hund’s principle is that electrons in different orbitals with the same energy would be positioned in such a way that they could be in the unpaired state of maximum number and the spin of the unpaired electrons will be one-way. And Pauli’s exclusion principle is that the value of four quantum numbers of two electrons in an atom cannot be the same. To write the orbital diagram of strontium(Sr), you have to do the electron configuration of strontium. Which has been discussed in detail above.

1s is the closest and lowest energy orbital to the nucleus. Therefore, the electron will first enter the 1s orbital. According to Hund’s principle, the first electron will enter in the clockwise direction and the next electron will enter the 1s orbital in the anti-clockwise direction. The 1s orbital is now filled with two electrons. Then the next two electrons will enter the 2s orbital just like the 1s orbital. The next three electrons will enter the 2p orbital in the clockwise direction and the next three electrons will enter the 2p orbital in the anti-clockwise direction.

The next two electrons will enter the 3s orbital. Then the next six electrons will enter the 3p orbital just like the 2p orbital. The 3p orbital is now full. So, the next two electrons will enter the 4s orbital just like the 1s orbital. The 4s orbital is now full. Therefore, the next five electrons will enter the 3d orbital in the clockwise direction and the next five electrons will enter the 3d orbital in the anti-clockwise direction. The 3d orbital is now full. so, the next six electrons will enter the 4p orbital just like the 3p orbital. The 4p orbital is now full. So the remaining two electrons will enter the 5s orbital just like the 4s orbital. This is clearly shown in the figure of the orbital diagram of strontium.

Strontium ion(Sr²⁺) electron configuration

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. 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.