What scientist described a positively charged core in the middle of the atom

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

The molecular formula for caffeine is cshion402. which of the following elements is not found in caffeine?

What was the procedure by which case united states vs lopez went to court