🤓 Based on our data, we think this question is relevant for Professor Freitag's class at CREIGHTON.

Problem

Naturally occurring boron consists of two isotopes: ^{10}B (19.9%) with an isotopic mass of 10.0129 amu and ^{11}B (80.1%) with an isotopic mass of 11.00931 amu.

What is the atomic weight of boron? Check your answer by looking at a periodic table.

Solution

We are asked to determine the atomic weight (average molecular mass) of a Boron (B) given ^{10}B (19.9%) with an isotopic mass of 10.0129 amu and ^{11}B (80.1%) with an isotopic mass of 11.00931 amu.

We will solve for Boron's average mass using their abundance.

**The formula for average mass is:**

$\overline{){\mathbf{Average}}{\mathbf{}}{\mathbf{molecular}}{\mathbf{}}{\mathbf{mass}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}{\sum _{}}{\mathbf{(}}{\mathbf{Mass}}{\mathbf{}}{\mathbf{isotope}}{\mathbf{}}{\mathbf{\times}}{\mathbf{}}{\mathbf{Fractional}}{\mathbf{}}{\mathbf{Abundance}}{)}}$

Isotopes

Ch.2 - Atoms & Elements → Isotopes

Ch.2 - Atoms & Elements → Isotopes