An element A has atomic number 14 and three isotopes 28^A, 29^A, and 30^A with relative abundances of 92.2%, 4.7% and 3.1% respectively, what is the relative atomic mass of the element?

An element A has atomic number 14 and three isotopes  28^A, 29^A, and 30^A with relative abundances of 92.2%, 4.7% and 3.1% respectively, what is the relative atomic mass of the element?

A. 28.109

B. 29.831

C. 28.958

D. 29.815

To find the relative atomic mass, use the weighted average of the isotopes.

Relative atomic mass = (28 * 92.2) + (29 * 4.7) + (30 * 3.1)/100

Calculate:

• (28 * 92.2 = 2581.6)

• (29 * 4.7 = 136.3)

• (30 * 3.1 = 93.0)

Sum:
2581.6 + 136.3 + 93.0 = 2810.9 

Divide by 100:

2810.9/100 = 28.109

✅ Correct answer: A. 28.109

PQN: 37