【】What element has the electron configuration 1s2 2s2 2p6 3s2 3p5 and it has how many valence electrons?
What element has the electron configuration 1s2 2s2 2p6 3s2 3p5 , and how many valence electrons do it has ?
Answer: Chlorine element has the electron configuration 1s2 2s2 2p6 3s2 3p5 , and it has seven valence electrons.
Explanation:
Given electron configuration is 1s2 2s2 2p6 3s2 3p5 .
Now count the number of electrons present here.Here we are getting 17 electrons (2 + 2+ 6+2+5 =17).The charge of an electron is negative and the charge of a proton is positive . For a neutral element , the number of electrons and protons is equal.So this element has 17 protons.
We know that the number of protons is called atomic number.So this element's atomic number is 17.From periodic table, we can say that chlorine element has the atomic number 17.So Chlorine element has the electron configuration 1s2 2s2 2p6 3s2 3p5 .
Explanation for valence electrons
Given electron configuration is the electron configuration 1s2 2s2 2p6 3s2 3p5 .
Now identify the outermost shell or valence shell.Here the outermost shell or valence shell is 3s2 3p5 .
After that, count the number of electrons present in the outermost shell or valence shell . Here we are getting seven electrons (2+5 = 7 ).So, it has seven valence electrons.
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