Question

Calculate the atomic weight of neon (Ne), composed of three naturally occurring isotopes with the following natural abundances and masses: a. \(90.51 \%\) Ne-20 (mass \(=19.992 \mathrm{amu}\) ) b. \(0.27 \% \mathrm{Ne}-21\) (mass \(=20.993 \mathrm{amu}\) ) c. \(9.220 \mathrm{Ne}-22(\) mass \(=21.991 \mathrm{amu})\)

Short answer

The atomic weight of neon is approximately 20.179 amu.

Step-by-step solution

Convert Percentage to Decimal

Convert the natural abundances of each isotope from percentage to decimal form by dividing by 100.

Calculate the Contribution of Each Isotope

Multiply the abundance (in decimal form) of each isotope by its respective atomic mass to obtain the contribution of each isotope to the atomic weight of neon.

Sum the Contributions

Add the contributions from each isotope to get the atomic weight of neon.

Key concepts

Isotopic Abundance

Understanding the concept of isotopic abundance is essential in calculating an element's atomic weight. Isotopic abundance refers to the percentage of an isotope naturally occurring within a sample of an element. Because elements in nature are often a mix of isotopes, knowing the relative amounts of each isotope allows scientists to determine average atomic masses.

For instance, in the case of neon, it has three naturally occurring isotopes: Ne-20, Ne-21, and Ne-22. By assessing the percentage of each isotope present, we can calculate neon's overall atomic weight. This is a critical step since isotopic abundance directly influences the calculated average atomic mass of the element.

Atomic Mass Unit (amu)

The atomic mass unit (amu) is a standard unit of mass that quantifies the mass of atoms and molecules. It is defined as one-twelfth of the mass of a carbon-12 atom, which is approximately equal to the mass of a single proton or neutron. The amu makes it convenient to express atomic and molecular masses on a scale suited for individual atoms and small molecules.

When we talk about an isotope's mass, such as Ne-20 with a mass of 19.992 amu, we're measuring how much one atom of Ne-20 weighs compared to the carbon-12 standard. This amu scale helps chemists and physicists perform calculations that involve the mass of atoms, like when determining the atomic weight of elements.

Natural Isotopes

Natural isotopes are various forms of an element's atoms that have the same number of protons but different numbers of neutrons. This difference in neutron count leads to variations in atomic mass, and thus isotopes of an element have slightly different properties. Most elements have multiple naturally occurring isotopes.

Each isotope of an element, like neon's Ne-20 and Ne-22, is part of the natural isotopic distribution found on Earth. These isotopes contribute to an element's average atomic mass, which is what we typically find on the periodic table. The concept of natural isotopes is significant in various scientific fields, including radiometric dating, medical diagnostics, and nuclear energy.

Chemical Education

Chemical education aims to impart knowledge about chemistry's fundamental principles, including the calculation of atomic weights. Educators strive to present these concepts clearly, helping students build a strong foundation for understanding chemical processes. A firm grasp of topics like isotopic abundance, atomic mass units, and natural isotopes allows students to explore more advanced areas of chemistry.

Effective chemistry education uses a mixture of theoretical explanation and practical application. For instance, exercises that involve calculating atomic weights with isotopic abundances are a practical way to apply these concepts. Clear explanations and step-by-step solutions like the one provided for neon's atomic weight calculation serve as valuable teaching tools, simplifying complex ideas into understandable chunks.