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).
A mole is a unit of measuring the quantity of anything. A single mole is set to the number of particles found in 12.000 grams of carbon-12. This number is 6.022 x 1023 carbon atoms. The number 6.022 x 1023 is known as Avogadro's Number. A mole of carbon-12 atoms has 6.022 x 1023 carbon-12 atoms.