How to Find the Valence Electrons for Selenium (Se)?
The 34th element of the periodic table is selenium. The element of group-16 is selenium and its symbol is ‘Se’. Selenium forms bonds through its valence electrons.
What are the valence electrons of selenium?
The 3rd element in group-16 is selenium. The valence electrons are the total number of electrons in the last orbit(shell).
The total number of electrons in the last shell after the electron configuration of selenium is called the valence electrons of selenium.
The valence electrons determine the properties of the element and participate in the formation of bonds.
How do you calculate the number of valence electrons in a selenium atom?
The valence electron has to be determined by following a few steps. The electron configuration is one of them. It is not possible to determine the valence electron without electron configuration.
Knowing the electron configuration in the right way, it is very easy to determine the valence electrons of all the elements.
However, valence electrons can be easily identified by arranging electrons according to the Bohr principle. Now we will learn how to determine the valence electron of selenium.
Step-1: Determining the total number of electrons in selenium
1st we need to know the total number of electrons in the selenium atom. To know the number of electrons, you need to know the number of protons in selenium.
And to know the number of protons, you need to know the atomic number of the selenium element. To know the atomic number we need to take the help of a periodic table.
It is necessary to know the atomic number of selenium elements from the periodic table. The atomic number is the number of protons. And electrons equal to protons are located outside the nucleus.
That is, we can finally say that there are electrons equal to the atomic number in the selenium atom. From the periodic table, we see that the atomic number of selenium is 34. That is, the selenium atom has a total of thirty-four electrons.
Step-2: Need to do electron configuration of selenium
Step-2 is very important. In this step, the electrons of selenium have to be arranged. We know that selenium atoms have a total of thirty-four electrons.
The electron configuration of the selenium shows that there are two electrons in the K shell, eight in the L shell, eighteen in the M shell, and six in the N shell.
That is, the first shell of selenium has two electrons, the second shell has eight electrons, the 3rd shell has eighteen electrons and the 4th shell has six electrons. The number of electrons per shell of selenium is 2, 8, 18, 6.
Step-3: Determine the valence shell and calculate the total electrons
The third step is to diagnose the valence shell. The last shell after the electron configuration is called the valence shell. The total number of electrons in a valence shell is called valence electrons.
The electron configuration shows that the last shell of selenium has six electrons. Therefore, the valence electrons of selenium are six.
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How many valence electrons does selenium ion(Se2-) have?
The elements that have 5, 6, or 7 electrons in the last shell receive the electrons in the last shell during bond formation. The elements that receive electrons and form bonds are called anions.
During the formation of a bond, the last shell of selenium receives two electrons and turns into a selenium ion(Se2-). That is, selenium is an anion element.
Se + 2e– → Se2-
The electron configuration of selenium ion(Se2-) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6.
This electron configuration shows that the selenium ion(Se2-) has four shells and the last shell has eight electrons and the selenium ion(Se2-) has acquired the electron configuration of krypton.
Since the last shell of a selenium ion has eight electrons, the valence electrons of selenium ion(Se2-) are eight.
What is the valency of selenium?
The ability of one atom of an element to join another atom during the formation of a molecule is called valency(valence). There are some rules for diagnosing valency.
The number of electrons in an unpaired state in the last orbit after the electron configuration of an atom is called the valency of that element.
The correct electron configuration of selenium(Se) in the ground state will be 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4px2 4py1 4pz1.
This electron configuration shows that the last shell of the selenium atom has two unpaired electrons. So in this case, the valency of selenium is 2. Valency is determined from the electron configuration of the element in the excited state.
When the selenium atom is excited, then selenium atom absorbs energy. As a result, an electron in the 4p orbital jumps to the 5s orbital.
Therefore, the electron configuration of selenium(Se*) in excited state will be 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4px1 4py1 4pz1 5s1.
Here, selenium has four unpaired electrons. So in this case, the valency of selenium is 4. The oxidation state of selenium is -2, +2,+4, and +6.
The oxidation state of selenium +6 has been used in Selenium trioxide (SeO3). The valency of selenium in this compound is 6. The oxidation states of selenium depend on the bond formation.