Why do groups among the among the main group elements display similar chemical behavior

Silver tarnishes as silver metal reacts with hydrogen sulfide, h2s, in the air. in this reaction, dark silver sulfide, au2s, covers the surface of silver. when silver is polished, this coating of silver sulfide can be removed from the surface. this makes the silver shiny again. enter the coefficients that balance the tarnishing reaction equation. (type 1 for no coefficient.)

What will most likely happen when two bromine atoms bond together?

Connect the whole numbers on the periodic table to indicate what they represent?