Which of the following samples has the greatest mass?
a)1.4 mol na
b) 1.02 _ 1024 atoms na
c) 23 g na
d) 6.02 _ 1023 atoms na

Atomic mass of Na: 23 g => 1 mol of Na = 23 g

Analysis of each choice:

A) 1. 4 mol = 1.4mol*23g/mol = 32.2 g

B) 1 mol of atoms = 6.02 x 10^23 atoms => 1.02 x 10^24 atoms / 6.02 x 10^23 atoms/mol = 1.69 mol

1.69mol*23g/mol = 38.87 g

C) 23 g

D) 6.02 x 10 ^23 atoms = 1 mol = 23 g.

Then the option B) is the right answer.