Name: atomic mass and mole calculations
Uploaded: 2023-06-23T15:38:52.000Z
Duration: 1 min 25 s
Channel: JoVE

Das Atomgewicht eines Elements, manchmal auch Atommasse genannt, entspricht ungefähr der Summe der Anzahl der Protonen und Neutronen. Dies wird in atomaren Masseneinheiten ausgedrückt, abgekürzt als amu oder Daltons, und wird in der Nähe seines chemischen Symbols im Periodensystem dargestellt.
Die meisten Elemente haben jedoch mehrere Isotope, die sich in der Anzahl der Neutronen und damit in ihrer Masse unterscheiden.
Für solche Elemente ist das Atomgewicht die durchschnittliche Masse aller Isotope eines Elements, gewichtet nach ihrer relativen Häufigkeit oder dem prozentualen Anteil jedes in der Natur vorkommenden Isotops.
Zum Beispiel hat Chlor zwei natürlich vorkommende Isotope. Die Masse von Chlor-35 beträgt 34,97 amu und die von Chlor-37 36,97 amu.
Multipliziert mit ihren relativen Häufigkeiten, 75,77 % für Chlor-35 und 24,23 % für Chlor-37, und addiert ergibt sich das endgültige Atomgewicht von 35,45 amu.
Da Chlor-35 in der Natur häufiger vorkommt als Chlor-37, liegt das Atomgewicht von Chlor bei nahezu 35 amu.

atomares gewicht

Protonen und Neutronen haben ungefähr die gleiche Masse, etwa 1,67 × 10-24 Gramm. Wissenschaftler haben diese Masse als eine atomare Masseneinheit (amu) oder ein Dalton definiert. Elektronen sind viel leichter als Protonen und wiegen nur 9,11 × 10-28 Gramm, oder etwa 1/1800 einer atomaren Masseneinheit. Daher tragen sie nicht viel zum gesamten atomaren Gewicht eines Elements bei. Das bedeutet, dass es üblich ist, die Masse der Elektronen bei der Berechnung des Atomgewichts zu ignorieren und das Gewicht des Atoms nur anhand der Anzahl von Protonen und Neutronen zu berechnen. Da jedoch die meisten natürlichen Elemente aus Isotopen bestehen, ist es wichtig, das Gewicht und die natürliche Häufigkeit der Isotope zu berücksichtigen, um das atomare Gewicht solcher Elemente zu bestimmen. In solchen Fällen wird das atomare Gewicht berechnet, indem man die Masse jedes Isotops mit seiner natürlichen Häufigkeit multipliziert und diese Werte anschließend addiert. Chemiker verwenden oft die Einheit „Mol„, um die Anzahl der Atome einer Verbindung zu bestimmen, die an einer chemischen Reaktion teilnehmen. Ein Mol eines Elements entspricht seinem atomaren Gewicht in Gramm, während ein Mol einer Verbindung die Summe der atomaren Gewichte ihrer Bestandteile ist, das als Molekulargewicht bezeichnet wird. Ein oft verwendetes Beispiel ist die Berechnung eines Mols Glucose mit der chemischen Formel C6H12O6. Das atomare Gewicht von Kohlenstoff (C) beträgt 12,011 amu, und da Glucose sechs Kohlenstoffatome enthält, ergibt dies ein Gesamtatomgewicht von 72,066 amu für den Kohlenstoffanteil. Bei der Berechnung von Wasserstoff (H) und Sauerstoff (O) ergibt sich das Molekulargewicht von Glucose zu 180,156 amu. Dieser Text ist teilweise angepasst von <a href="https://openstax.org/books/biology-ap-courses/pages/2-1-atoms-isotopes-ions-and-molecules-the-building-blocks?query=atomic%20mass&target=%7B%22type%22%3A%22search%22%2C%22index%22%3A0%7D#fs-idp140338797859808">Openstax, Biology for AP</a><a href="https://openstax.org/books/biology-ap-courses/pages/2-1-atoms-isotopes-ions-and-molecules-the-building-blocks?query=atomic%20mass&target=%7B%22type%22%3A%22search%22%2C%22index%22%3A0%7D#fs-idp140338797859808">® </a><a href="https://openstax.org/books/biology-ap-courses/pages/2-1-atoms-isotopes-ions-and-molecules-the-building-blocks?query=atomic%20mass&target=%7B%22type%22%3A%22search%22%2C%22index%22%3A0%7D#fs-idp140338797859808">courses. Section 2.1 Atoms, Isotopes, Ions, and Molecules: The Building Blocks</a> and <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/2-4-inorganic-compounds-essential-to-human-functioning?query=mole&target=%7B%22type%22%3A%22search%22%2C%22index%22%3A0%7D#fs-id1218107">Openstax, Anatomy and Physiology 2e, Section 2.4 Inorganic compounds Essential to Human Functioning</a>

Atomares Gewicht

Protonen und Neutronen haben ungefähr die gleiche Masse, etwa 1,67 × 10-24 Gramm. Wissenschaftler definieren diese Massenmenge willkürlich als eine Atommasse ...

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Atomic Weight

atomic mass and mole calculations

Atomic mass and mole calculations help explain how much matter is in atoms and compounds. Protons and neutrons have about the same mass, about 1.67 × 10 -24 grams. Scientists define that mass as one atomic mass unit, or amu, also called one Dalton.

Electrons are much lighter than protons. They weigh only 9.11 × 10 -28 grams, or about 1/1800 of an atomic mass unit. Because of that small mass, electrons do not add much to an element’s overall atomic mass. When chemists calculate atomic mass, they usually ignore electrons and use only the protons and neutrons.

Many naturally occurring elements are made of isotopes, which are atoms of the same element with different masses. For these elements, atomic mass must include each isotope’s mass and its natural fractional abundance. Chemists find this by adding the masses of all the isotopes after multiplying each one by how common it is.

Chemists also use the mole to count atoms and compounds in reactions. A mole of an element is its atomic weight in grams. A mole of a compound is the sum of the atomic weights of its parts, and that total is called the molecular weight. Glucose, C6H12O6, is a common example. Carbon has an atomic weight of 12.011 grams, and six carbons in glucose give 72.066 grams. Doing the same for hydrogen and oxygen gives glucose a molecular weight of 180.156 grams.

Atomic Mass and Mole Calculations

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Atomic Mass and Mole Calculations

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