Question

An unknown element is found to have three naturally occurring isotopes with atomic masses of 34.9689 (76.000%), 36.9659 (23.988%) and 35.9683 (0.012%) Which of the following is the unknown element?

Answer 1

Chlorine (35.44 amu)

Step-by-step explanation:

An unknown element is found to have three naturally occurring isotopes with atomic masses of 34.9689 (76.000%), 36.9659 (23.988%) and 35.9683 (0.012%).

We need to find the mass of the unknown element. When abundances is given, then atomic mass is given by :

`M=34.9689 (76.000\%)+36.9659 (23.988\%) +35.9683(0.012\%)\\\\=34.9689 ((76)/(100))+36.9659 ((23.988)/(100)) +35.9683((0.012)/(100))\\\\=35.44\ \text{amu}`

So, the atomic mass of the unknown element is 35.44 amu and it is chlorine.