Me
how can you tell if two objects are thermal equilibrium?
the objects are the same size.
the objects have the same temperature.
the objects temperature are changing.
the objects are touching each other.

Two objects in physical contact with each other are in thermal equilibrium when they reach the same temperature and an exchange of heat energy no longer occurs. According to HyperPhysics, the relation of thermal equilibrium follows the Zeroth Law of Thermodynamics, which states that “if two systems are at the same time in thermal equilibrium with a third system, they are in thermal equilibrium with each other.” 

Is there any opitions? if you have the periodic table, the noble gases are 8a family, the halogen are the 7a family, and the nonmetal are  carbon, nitrogen, phosphorus, oxygen, sulfur, selenium, fluorine, chlorine, bromine, iodine and astatine.