What is the greatest number of theoretical cross-linkages possible by vulcanizing 100 g of polyisoprene chains?

(a) the number-average molecular weight.  22,500 * 0.04 + 37,500 * 0.07 + 52,500 * 0.16 + 67,500 * 0.26 + 82,500 * 0.24 + 97,500*0.12 + 112,500*0.08 + 127,500 * 0.03 = 73,800 
(b) the weight-average molecular weight.  22,500*0.01 + 37,500*0.04 + 52,500 * 0.11 + 67,500 * 0.24 + 82,500 * 0.27 + 97,500 * 0.16 + 112,500 * 0.12 + 127,500 * 0.05 = 72,000

Bismuth (Bi) , Nitrogen family

Explanation:

As the element has 5 valence electrons in the sixth energy level, which mens it belongs to 6th period as the valence electron has entered the 6th energy level.

Now as the electrons are  filled according to afbau's rule , the electronic configuration of the element will be :

Now as the atomic number of element is equal to the number of electrons in a neutral atom , the atomic number is 83 and the element is Bismuth (Bi). As the last electron enters p -subshell , it is  a p block element. It lies in group 15 which is nitrogen family.