Selenium, the 34th element of the periodic table, belongs to Group 16 and is represented by the symbol ‘Se’. It forms bonds through its valence electrons, which are crucial in determining the element’s properties.
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Understanding the Valence Electrons of Selenium
Valence electrons are the electrons in the outermost shell or orbit of an atom. For selenium, being the 3rd element in Group 16, its valence electrons are determined by the total number of electrons in its last shell.
The valence electrons play a significant role in the element’s participation in bond formation and its overall characteristics.
Calculating the Number of Valence Electrons in a Selenium Atom
Determining the valence electrons involves understanding the electron configuration of selenium. The electron configuration provides essential information for identifying the valence electrons of any element.
By arranging the electrons based on the Bohr principle, we can easily determine the valence electrons of selenium.
Step 1: Total Number of Electrons in Selenium
To determine the total number of electrons in a selenium atom, we start by knowing the atomic number, which equals the number of protons in the element. Consulting the periodic table, we find that selenium has an atomic number of 34, meaning it has 34 electrons.
Step 2: Electron Configuration of Selenium
Next, we arrange the electrons in selenium. The electron configuration of selenium reveals that it has 2 electrons in the K shell, 8 in the L shell, 18 in the M shell, and 6 in the N shell. This translates to 2, 8, 18, 6 electrons per shell, respectively.
Step 3: Determining the Valence Shell and Valence Electrons
The valence shell is the last shell after the electron configuration. In the case of selenium, the electron configuration shows that the last shell contains 6 electrons, identifying selenium’s valence electrons as 6.
Valence Electrons of Selenium Ion (Se2-)
Elements with 5, 6, or 7 electrons in the last shell gain electrons during bond formation, making them anions. Selenium, during bond formation, acquires two additional electrons, resulting in the formation of a selenium ion (Se2-). Therefore, selenium is considered an anion element.
The electron configuration of a selenium ion (Se2-) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6. This configuration indicates that the selenium ion has four shells, with the last shell containing eight electrons, giving the selenium ion the electron configuration of krypton. As a result, the valence electrons of a selenium ion (Se2-) amount to eight.
Valency of Selenium
Valency, also known as valence, refers to the ability of an atom to form bonds with another atom during molecule formation. The valency of an element can be determined by examining the number of electrons in an unpaired state in the last orbit after electron configuration.
In the ground state, the correct electron configuration for selenium (Se) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4px2 4py1 4pz1. This configuration reveals that the selenium atom has two unpaired electrons, leading to a valency of 2. The valency is assessed based on the element’s electron configuration in an excited state.
When the selenium atom is excited, it absorbs energy, causing an electron in the 4p orbital to jump to the 5s orbital. In this excited state, the electron configuration for selenium (Se*) becomes 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4px1 4py1 4pz1 5s1. With four unpaired electrons, the valency of selenium in this case is 4.
Selenium exhibits oxidation states of -2, +2, +4, and +6. For instance, in Selenium trioxide (SeO3), selenium has an oxidation state of +6, and its valency in this compound is 6. The oxidation states of selenium depend on the bond formations it engages in.
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