Her behavior has been reinforced (i.e. strengthened). Reinforcement can be external or internal and can be positive or negative. If a child wants approval from parents or peers, this approval is an external reinforcement, but feeling happy about being approved of is an internal reinforcement.
It remained to define the unit of amount of substance by fixing the corresponding mass of carbon 12; by international agreement, this mass has been fixed at 0.012 kg, and the unit of the quantity amount of substance was given the name mole (symbol mol).
The mole is a unit of measurement used to express the amount of a chemical substance. It is defined as the amount of any substance that has exactly the same number of atoms, molecules, particles or entities as there are in 12 grams of pure Carbon-12.