Answer:
a. The first energy level has two, the second has eight, and the third has five.
Explanation:
In the periodic table , all of the elements are arranged according to the atomic number , the phosphorus is groups at position 15 and hence the atomic number is 15 .
The electrons of the elements are arranged according to the stability of the electrons , which is decided by the octet rule , where the stable electronic configuration is - 2 , 8 , 8 , 18...
i.e. ,
In the first shell maximum two electrons can reside , and in the second shell , maximum eight electrons can reside ,and so on.
Hence , determining the electron configuration as follows -
P ( 15 ) - 2 , 8 , 5 .