How to determine the group of an element based on an electron configuration

You can easily predict the group of any element by it's valence shell configuration. If the valence e confgn is ns1 then it belongs to 1 group if it is ns2 then it is 2 group element. For p block elements it is 10+ no of es of ns& np. Eg. Cl 3s2 3p5. So group no is 17. For d block elements group no is equal to ns+ (n-1) d es. For e.g. Cr 4s1 3d5 . Group no is 6. For f block elements group no is always 3.

Explanation:

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.