Question

Chlorine, Cl, has a(n) _______ ________ ________ of 35.45 amu.

A. Atomic mass number.
B. Atomic number.
C. Atomic mass.

Answer 1

Chlorine has an atomic mass of 35.45 amu

Answer 2

The atomic mass of chlorine (35.45 amu) accounts for the relative abundances and atomic masses of its two stable isotopes, chlorine-35 and chlorine-37. Correct answer to the student's question is atomic mass.

Step-by-step explanation:

The atomic mass of chlorine, Cl, with an average atomic mass of 35.45 amu is because chlorine has two naturally occurring isotopes: chlorine-35 and chlorine-37. Chlorine-35 has an atomic mass of 34.969 amu and accounts for about 75.77% of chlorine atoms, whereas chlorine-37 has an atomic mass of 36.966 amu and makes up approximately 24.23%. The average atomic mass of chlorine is calculated by the formula:

Average atomic mass = (% abundance of Cl-35 × atomic mass of Cl-35) + (% abundance of Cl-37 × atomic mass of Cl-37)

Applying this to chlorine gives us:

(0.7577 × 34.969 amu) + (0.2423 × 36.966 amu) = 35.45 amu.

This value is rounded following significant figure rules to arrive at the atomic mass listed on the periodic table for chlorine. Therefore, the correct statement is: Chlorine, Cl, has a(n) atomic mass of 35.45 amu.