Can someone explain covalent bonding a little further ?

When will le chatelier's principle come into effect? at the beginning of a reaction, when there are only reactants when a reaction has reached chemical equilibrium when a catalyst is added to a reaction mixture when a reaction is occurring but not yet at equilibrium

How can the periodic table be used to predict the behavior of elements?

The diagram shows the relationship between scientific disciplines.the names of some scientific disciplines have been removed from the boxes. which scientific discipline belongs in the blue box? a.physics b.biology c.chemistry d.metallurgy