# Silicon has three naturally occurring isotopes: Si-28 has a percent abundance of 92.23% and a mass of 27.977 amu, Si-29 that has a 4.68% abundance and a mass of 28.976 amu, and Si-30 that has a 3.09% abundance and a mass of 29.974 amu. Calculate the atomic mass for silicon using the weighted average mass method.

Question

Silicon has three naturally occurring isotopes: Si-28 has a percent abundance of 92.23% and a mass of 27.977 amu, Si-29 that has a 4.68% abundance and a mass of 28.976 amu, and Si-30 that has a 3.09% abundance and a mass of 29.974 amu. Calculate the atomic mass for silicon using the weighted average mass method.

check_circle

Step 1

The average atomic mass of silicon isotopes can be calculated as

Isotope = Si-28

amu =27.9769

Abundance (%) =92.18

Isotope = Si-29

amu =28.9765

Abundance (%) =4.71

Isotope =Si-30

amu =29.9738

Abundance (%) =3.12

Step 2

Multiple the amu by the percentage of occurrence to arrive at an average atomic mass

27.977 × 0.9223 + 28.976 × 0.0468+29.974×.0309

25.8031 + 1.3560 + 0.9261= 28.0852

...

### Want to see the full answer?

See Solution

#### Want to see this answer and more?

Solutions are written by subject experts who are available 24/7. Questions are typically answered within 1 hour.*

See Solution
*Response times may vary by subject and question.
Tagged in

### Chemistry 