Multiple Choice
Which of the following is closest to the atomic mass of a magnesium (Mg) atom?
2. Atoms & Elements
Atomic Mass
Multiple Choice
How is an atomic mass unit (amu) defined?
A
It is the mass of a single proton.
B
It is the mass of a hydrogen atom.
C
It is the average mass of all naturally occurring isotopes of an element.
D
It is defined as one twelfth the mass of a carbon-12 atom.
Verified step by step guidance1
Understand that the atomic mass unit (amu) is a standard unit of mass used to express atomic and molecular weights.
Recognize that the amu is not defined as the mass of a single proton or a hydrogen atom, nor as the average mass of isotopes of an element.
Recall that the amu is based on the carbon-12 isotope, which is a stable isotope of carbon with 6 protons and 6 neutrons.
Know that the atomic mass unit is defined as exactly one twelfth (1/12) of the mass of a single carbon-12 atom.
This definition provides a consistent scale for comparing atomic masses across different elements and isotopes.
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