Is atom a basic unit of mass?

Answer 1

The International System of Units (SI Units) specifies the basic unit of mass to be the kilogram (kg). All other units of mass are derived from this official standard.

There is, however something called an Atomic Mass Unit (AMU). It is offically recognized by the International System of Units but is a measured quantity, not a defined quantity.

The AMU equals one twelfth of the mass of an atom of carbon-12 and has a value of 1.660538×10−27 kg.

Answer 2

No, an atom is not a basic unit of mass. The basic unit of mass in the International System of Units (SI) is the kilogram, which is defined by a physical prototype known as the International Prototype of the Kilogram. An atom is the smallest unit of an element that retains the chemical properties of that element.