Average Atomic Mass Lecture Flashcards

Vocabulary practice flashcards covering definitions, formulas, subatomic particle mass values, and practice calculation results from the Average Atomic Mass lecture notes.

Average Atomic Mass

The average mass of ALL of the isotopes of an element on Earth!

Weighted Average (in atomic mass)

An average calculation found on the periodic table that takes into account how abundant (or common) each different isotope is, with units in $amu$.

Average Atomic Mass Formula

$$\text{Average atomic mass} = (\text{mass of isotope 1})(\text{abundance decimal of isotope 1}) + (\text{mass of isotope 2})(\text{abundance decimal of isotope 2}) + \dots$$

Subatomic Particle Mass Comparison Table

A reference table listing the mass number, relative mass (in $u$), and actual mass (in $g$) for electrons, protons, and neutrons.

Electron (Mass Properties)

Mass number: $\approx 0\,amu$; Relative mass: $0.0005486\,u$; Actual mass: $9.09 \times 10^{-28}\,g$.

Proton (Mass Properties)

Mass number: $1\,amu$; Relative mass: $1.007276\,u$; Actual mass: $1.673 \times 10^{-24}\,g$.

Neutron (Mass Properties)

Mass number: $1\,amu$; Relative mass: $1.00866\,u$; Actual mass: $1.675 \times 10^{-24}\,g$.

Calculated Atomic Mass of Bromine (Practice #1)

$79.91\,amu$ (calculated from bromine isotopes with masses of $78.92\,amu$ at $50.69\%$ abundance and $80.92\,amu$ at $49.31\%$ abundance, rounded to the hundredths place).

Calculated Atomic Mass of Element X (Practice #2)

$10.81\,amu$ (calculated from natural isotopes with mass $10.012$ at $19.91\%$ abundance and mass $11.009$ at $80.09\%$ abundance, rounded to the hundredths place).

Percent Abundances of Rubidium Isotopes (Practice #3)

Rubidium-85: $71.85\%$ and Rubidium-87: $28.15\%$ (calculated given an atomic mass of $85.47\,amu$ and exact isotope masses of $84.907596\,amu$ and $86.905287\,amu$, rounded to the hundredths place).

Percent Abundances of Copper Isotopes (Practice #4)

Copper-63: $69.2\%$ and Copper-65: $30.8\%$ (calculated given an atomic mass of $63.546\,amu$ and exact isotope masses of $62.93$ and $64.93$, rounded to the tenths place).