8which elements have the most similar chemical properties?
(1) si, as, and te (3) mg, sr, and ba
(2) n2, o2, and f2 (4) ca, cs, and cu

Silicon, Arsenic, and Tellurium all sit on the metal/nonmetal boundary

Magnesium, Strontium, and Barium are in the same group (Group 2)

Nitrogen, Oxygen, and Flourine are all non-metals in the same period

Calcium, Caesium, and Copper start with the same letter

So (3) Mg, Sr and Ba is the correct answer

High-energy and unstable.

While unproven, it uses facts to support part of a conclusion. it is still factual and has predictive power, however.