Element X has two naturally-occurring isotopes. X-10 has a 19.9% abundance and X-11 has an 80.1% abundance. What is most likely the identity of element X?

The identity of element X is Boron (R. A. M = 10.81)

Explanation:

We are given;

Element X,

First Isotope, X-10, with an abundance of 19.9% Second isotope, X-11 with an abundance of 80.1%

We are required to identify the element X

To identify the element we need to determine it R. A. M.

Then, how do we get R. A. M of an element?

R. A. M. = ((Mass of isotope-1 * R. abundance) + (mass of isotope-2 * R. abundance)) : 100

Therefore, in this case;

R. A. M. of X = ((mass of X-10 * R. abundance) + (mass of x-11 * R. abundance)) : 100

Thus;

R. A. M of X = ((10 * 19.9) + (11 * 80.1)) : 100

= 10.81

Thus, the relative atomic mass of X is 10.81.

The identity of element X is Boron. (Boron has an R. A. M of 10.81)