CHEM.6.D

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The student is expected to calculate average atomic mass of an element using isotopic composition; and
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Knowledge and Skills Statement

Science concepts. The student understands the development of atomic theory and applies it to real-world phenomena.

a theory of the nature of matter: all material substances are composed of minute particles or atoms of a comparatively small number of kinds and all the atoms of the same kind are uniform in size, weight, and other properties

the average mass of all isotopes of an element, given on the periodic table

a pure substance that is made up of one type of atom

the percentage of a sample that is composed of each isotope of an element

detectable events that are observed through the senses or technology; can be explained through scientific laws, ideas, principles, and theories

Research

Erler, Dirk, Luke Nothdurft, Mardi Mcneil, and Charly Moras."Tracing Nitrate Sources Using the Isotopic Composition of Skeletal-Bound Organic Matter from the Calcareous Green Algae Halimeda." Coral Reefs 37, no. 4 (2018):1003–1011. https://doi.org/10.1007/s00338-018-01742-z

Summary:  Here we adapt the persulphate/denitrifier protocol, previously developed for scleractinian corals, to analyse the d15N of organic material in the skeletons of the calcareous macroalgae Halimeda (hereafter referred to as d15N-SOM). Our results demonstrate that in low-nutrient environments, Halimeda skeletal material, including historical material obtained from sediment cores, can provide a reliable proxy record of d15N–NO3 - at the base of the food web. This technique holds much promise for reconstructing spatial and temporal patterns of N supply to coral reef systems worldwide.

Research

Aléon, J., Dan Lévy, Alice Aleon-Toppani, Helene Bureau, Hicham Khodja, and François Brisset. "Determination of the Initial Hydrogen Isotopic Composition of the Solar System." Nature Astronomy 6, no. 4 (2022): 458-463. https://doi.org/10.1038/s41550-021-01595-7

Summary:  The initial isotopic composition of water in the Solar System is of paramount importance to understanding the origin of water on planetary bodies but remains unknown, despite numerous studies1–5 . Here we use the isotopic composition of hydrogen in calcium–aluminium-rich inclusions (CAIs) from primitive meteorites, the oldest Solar System rocks, to establish the hydrogen isotopic composition of water at the onset of Solar System formation. We propose that the isotopic composition of inner Solar System water was established during the collapse of the protosolar cloud core owing to a massive admixture of interstellar water.