Question

How many electrons can occupy the S orbital at each energy level?

Answer 1

An electron shell is basically an orbit in which electrons revolve around an atomic center called nucleus. Now In atomic chemistry shells are made up of subshells, subshells are made up of orbitals which in turn consist of electrons in them. In order to find the number of electrons in a particular orbital we will firstly find the maximum number of electrons which can be present in the subshell and then divide it by the total orbitals present in the subshell.

Complete answer:
Firstly, we need to find out the maximum number of electrons which can be present in the S subshell.
Maximum number of electrons which in a subshell is given by = $2(2l\,+\,1)$
Here $l=$Azimuthal quantum number
We know that the value of $l$for S subshell is 0
So, maximum number of electrons in s subshell = $2(2\times 0\,+\,1)\,=\,2$electrons
Now we need to find out total orbitals in the S subshell.
For this, we will use the formula as mentioned below
Total number of orbitals in a subshell = $2l\,+\,1$
$\therefore$ Total number of orbitals in S subshell = $2\times \,0\,+\,1\,=\,1$orbital
Now number of electrons in one orbital of subshell is given by = $\dfrac{Total\,number\,of\,electrons\,in\,subshell}{Total\,Number\,of\,electrons}$
Hence total number of electrons in s orbital at each energy level = $\dfrac{2}{1}\,=\,2\,electrons$
Therefore, two electrons with opposite spins are present in the orbital of each energy level.

Note: Always learn the basic formulas of calculating the shell, subshell, orbital and electrons. Whenever there is confusion then cross check the answer by drawing a simple rough diagram, as depicted below-

$\uparrow \downarrow$

This is a s orbital and at maximum it can have 2 electrons.