Question

How many electrons are present in the outermost shell in a silicon atom?

Answer 1

Hint:The Silicon belongs to the group in which C is placed and has an atomic number 14. The K shell accommodates 2 electrons only, L shell accommodates 8 electrons and M shell can have a maximum of 18 electrons.

Complete step-by-step answer: So in the question it is asked how many valence electrons are present in a Si atom. From the time we study about the periodic table and the elements present in them, we are always concerned of the number of subatomic particles present in the atoms and how they are arranged specially we are concerned about the arranged of the electrons since we know that the other two –protons and neutrons are present in the atomic nucleus and they do not have much role in the chemical reactions. Electrons are the species which are involved in the chemical reactions,
Specially valence electrons are of great concern since they give an idea about the combining capacity of the atom and the number of valence electrons gives an idea of various oxidation states that can be shown by the element or atom.
Now let’s move on to the solution part of the given question. In the hint part it is given that Si belongs to the group in which C belongs to C belongs to group 14 so Si also belongs to group 14 or main group IV and hence the number of valence electrons will be four as the main group number refers to the valence electrons present in an element.
If we do not know the group number, then we could write the electronic configuration of Si and then find the valence electrons.
Since the atomic number of Si is 14, there are 14 electrons, now let’s write the electronic configuration of Si.
$\text{Electronic}\text{configuration}\text{of}\text{Si=1}{\text{s}}^{\text{2}}\text{2}{\text{s}}^{\text{2}}\text{2}{\text{p}}^{\text{6}}\text{3}{\text{s}}^{\text{2}}\text{3}{\text{p}}^{\text{2}}$
As we can see in the electronic configuration that the outermost shell is the $3^{rd}$shell and the total number of electrons present in the $3^{rd}$shell will give the valence electrons.

Here the total number of outermost shell electrons present is four.

Note:Alternate method:
If we know the total number of electrons or atomic number then distribute the number in different shells. The first shell accommodates 2 electrons, second one 8 electrons, and third shell 18 electrons etc.
So here if we distribute the electrons, K=2, L=8, M=4
The third shell is the outermost shell and it has four valence electrons in them.
We know that the number of valence electrons are similar for an entire group present in a periodic table and because of this they will possess similar chemical properties.