I am not 100% sure but I think it is circulation/orbitiation.
Answer:
In Chemistry, Dobereiner triads are defined as, any of several sets of three chemically same elements, the atomic weight of one, which is nearly equal to the mean of the atomic weights of the other two elements.
An ion is an element that bears only one electric charge, either positive or negative. An isotope is an element with the same number of protons but a different number of neutrons. An electron is a negatively charged subatomic particle. A dipole fits the characteristics. Hence, the answer is B.
Two examples of chemical change in common items are - wood burning and rust forming on a nail due to oxidation.
