<u>Answer: </u>Value of A is 2 and value of B is 1.
<u>Explanation:</u>
Lithium is the third element of the periodic table. It belongs to the Period 2 and Group 1 and is considered as an alkali metals.
To write the electronic configuration, we need to find the number of electrons this element contain, which is equal to the atomic number.
Number of electrons = Atomic number = 3
So, the electronic configuration will be: 
The s-orbital in total can contain only 2 electrons.
Hence, the value of A is 2 and value of B is 1.