2.2 chromium has four naturally-occurring isotopes: 4.34% of 50cr, with an atomic weight of 49.9460 amu; 83.79% of 52cr, with an atomic weight of 51.9405 amu; 9.50% of 53cr, with an atomic weight of 52.9407 amu; and 2.37% of 54cr, with an atomic weight of 53.9389 amu. on the basis of these data, confirm that the average atomic weight of cr is 51.9963 amu.

Average atomic mass  = 51.9963 amu

Explanation:

Given data:

Abundance of Cr⁵⁰ with atomic mass= 4.34% ,  49.9460 amu

Abundance of Cr⁵² with atomic mass = 83.79%,  51.9405 amu

Abundance of Cr⁵³ with atomic mass =9.50%,  52.9407 amu

Abundance of Cr⁵⁴ with atomic mass  = 2.37%,   53.9389 amu

Average atomic mass = 51.9963 amu

Solution:

Average atomic mass = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass +n)  / 100

Average atomic mass  = (4.34×49.9460)+(83.79×51.9405) +(9.50×52.9407)+ (2.37×53.9389) / 100

Average atomic mass =  216.7656 + 4352.0945 + 502.9367 +127.8352 / 100

Average atomic mass  = 5199.632 / 100

Average atomic mass  = 51.9963 amu

the answer is 303.15 or 303