Which pair of species have the most nearly
identical atomic and molecular properties?
1. 35/17Cl and 80/35Br
2. 7/3Li and 9/4Be
3. 23/11Na and 23/11Na+
4. 19/9F and 19/9F−
5. 12/6C and 13/6C
Since Electro Negativity will change their reactions the answer should be number 5. 12/6c and 13/6c. This is due to the fact that there is only one neutron difference between the two.
