Question

Which best describes the definition for the atomic mass of an element?

It is a weighted average of the masses of an element’s isotopes.

It is a ratio based on the mass of the carbon-12 atom.

It is the sum of the protons and neutrons in one atom of the element.

It is twice the number of protons in one atom of the element.

Answer 1

It is a weighted average of the masses of an element’s isotopes.

Step-by-step explanation:

The best definition of the atom mass of an element is that it is a weighted average of the masses of an element's isotopes.

• Isotopes of an element have the same electronic configuration but differ in only their masses.
• The atomic mass of an element can be derived from the geonormal abundances of this isotopes.
• It is the average of all the isotopes of an element.

Atomic mass = ∑m
`_(i)` a
`_(i)`

where m
`_(i)` is the mass of the isotope i

a
`_(i)` is the abundance of the isotope i