An element x atomic number 3, relative atomic number 6.94 and consists of two isotopes of mass numbers 6 and 7 respectively.

What is the mass number of the more abudant isotope of x?

7

Explanation:

Atomic number of X = 3

Atomic mass of X = 6.94 amu

1st isotope atomic mass = 6 amu

2nd isotope atomic mass = 7 amu

Which is more abundant isotope = ?

Explanation:

we know there are two naturally occurring isotopes of given element X, X-6 and X-7.

First of all we will set the fraction for both isotopes

x for the isotopes having mass 6

1-x for isotopes having mass 7

The average atomic mass of X = 6.94 amu

we will use the following equation,

6x + 7 (1-x) = 6.94

6x + 7 - 7x = 6.94

6x - 7x = 6.94 - 7

-1x = - 0.06

x = - 0.06/-1

x = 0.06

0.06 * 100 = 6%

6% is abundance of X-6 because we solve the fraction x.

now we will calculate the abundance of X-7.

(1-x)

1-0.06 = 0.94

0.94 * 100 = 94%

94% for X-7.