Question

An unknown element is found to have three naturally occurring isotopes with atomic masses of 35.9675 (0.337%), 37.9627 (0.063%) and 39.9624 (99.600%). Which of the following is the unknown element? A) Ar B) K C) CI D) Ca E) None of the above could be the unknown element.

Answer 1

The answer to your question is letter A, Argon

Step-by-step explanation:

Isotope Atomic mass Percent (%)

1 35.9675 0.337

2 37.9627 0.063

3 39.9624 99.6

Average atomic mass = (Mass isotope 1)(percent 1) + (Mass isotope 2)(percent

2) + (Mass isotope 3)(percent 3)

Average atomic mass = (35.9675)(0.00337) + (37.9627)(0.00063) +

(39.9624)(0.996)

Average atomic mass = 0.1212 + 0.0239 + 39.8025

Average atomic mass = 39.9476

Theoretical Atomic mass

a) Ar 39.95

b) K 39.10

c) Cl 35.45

d) Ca 40.08