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How many valence electrons would be found in an atom with the atomic number of 51?
(A) 5
(B) 51
(C) 8
(D) None of the above

Last updated date: 20th Jun 2024
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Hint: To solve this problem, firstly we have to understand what valence electrons are, and the concept behind them. We will be learning the relation of valence electrons with atomic number, chemical properties of the elements and the electronic configuration of the compounds. And by this knowledge we will be approaching our answer.

Complete step by step solution:
Electrons which are present in the outer shell of an atom are called valence electrons. For example, the atomic number of sodium is 11 and the electronic configuration of sodium is 2,8,1 and in this the third shell is the outermost shell i.e., valence shell which is having one electron. So, sodium has 1 valence electron.
Now, the atomic number of an atom is 51. The valence electrons as we know are present in the last shell of an atom. The atomic number of Antimony is 51 and its symbol is Sb i.e. stibium. The electronic configuration of Sb will be 2,8,18,18,5. So, the number of valence electrons present in the outer shell of Sb is 5.

Hence, the correct option is A -5.

Hence, all the elements having similar chemical properties will have the same valence electrons. The very first element of the period has one valence electron. Also, the elements which are present in the same group show similar properties as they have similar electronic configuration i.e., they have the same number of valence electrons.

Note - The chemical properties of an element can be determined by the presence of electrons in the outermost shell or valence electrons. And in the 1st period of the periodic table we observe that the number of valence electrons increases from 1 to 2. There is a total of 7 Periods 1,2,3,4,5,6 and 7. And a total of 18 groups 1,2,3,4, 5,….,17,18.