Concept:Atomic weight is the average mass of an atom of an element.
It is measured in atomic mass units (amu) or g/mol and equals the weighted average of its natural isotopes.
Explanation:Lithium has the symbol Li and atomic number 3.
Its atomic weight is the weighted average of its naturally occurring isotopes.
This standard value is taken from the periodic table.
The atomic weight of Lithium is 6.941 amu, which is also written as 6.941 g/mol.
This value can vary slightly between 6.9387 and 6.9959 depending on the source.
It is approximately equal to the total number of protons and neutrons in the atom.
The unit amu (atomic mass unit) is also called dalton.
Comparing the options: 9.012 amu is Beryllium, 4.003 amu is Helium, and 10.811 amu is Boron.
Only 6.941 amu matches Lithium.
Answer:A. 6.941 amu, g/mol