If you look at the periodic table today which elements would best represent a triad as predicted by Dobereiner? A. Hydrogen Oxygen Nitrogen
B. Nickel Copper Zinc
C. Aluminum Gallium Indium
D. Neptunium Plutonium Americium
E. All of them are triads
HELP ME PLEASE

 B. Nickel Copper Zinc

Explanation:

Dobereiner's triads was a group of three elements. Dobereiner said that the relative atomic mass of the middle element in each triad was average of the relative atomic masses of the other two elements.

Thus if A, B and C forms Dobereiner's triads, the mass of B is average of mass of A and C.

A. Hydrogen Oxygen Nitrogen:

mass of oxygen = 15.999

mass of oxygen according to Dobereiner =

B. Nickel Copper Zinc

mass of copper = 63.5

mass of copper according to Dobereiner =

C. Aluminum Gallium Indium

mass of gallium = 69.72

mass of gallium according to Dobereiner =

D. Neptunium Plutonium Americium

mass of Plutonium = 244

mass of Plutonium according to Dobereiner =

it's c. elements are placed in rows based on how may valencies electrons have.