Answer & explanation:
The atomic mass of the atom is expressed in u. Indicates how many times the mass of the atom is greater than 1/12 of the mass of the carbon atom (A = 12).
When we measure a quantity, we compare it with another as a reference. To measure the mass of our body we use the kilogram (kg) as the standard unit. If the person has a mass of 80kg it means that his mass is 80 times greater than the mass of 1kg.
Chemistry, in practice, is not interested in knowing the mass of an isolated atom, but for science it is important to know the mass of atoms compared to the mass of another atom taken as standard. Carbon was then the element that has its standardized mass (A = 12).
The mass of an atom is expressed by employing a very small unit called the atomic mass unit (u). When the mass of an element X is stated to be 24u, it means that its mass is 24 times greater than the 1/12 mass of the carbon atom (A = 12). In other words, the atomic mass of element X is twice the atomic mass of carbon.
