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

元素の原子量は、原子質量と呼ばれることもあり、陽子と中性子の数の合計にほぼ等しくなります。これは原子質量単位で表され、アムまたはダルトンと略され、周期表の化学記号の近くで表されます。
しかし、ほとんどの元素には、中性子の数や質量が異なるいくつかの同位体があります。
このような元素の場合、原子量は、元素のすべての同位体の平均質量であり、それらの相対的な存在量または自然界に見られる各同位体の割合に従って重み付けされます。
たとえば、塩素には2つの天然同位体があります。塩素-35の質量は34.97 amu、塩素-37の質量は36.97 amuです。
それらの相対的な存在量である塩素-35の75.77%と塩素-37の24.23を掛け合わせると、最終的な原子量は35.45 amuになります。
塩素-35は塩素-37よりも自然界に豊富に存在するため、塩素の原子量は35 amuに近いです。

原子量

陽子と中性子はほぼ同じ質量を持ち、約1.67×10-24グラムです。科学者は、この質量を1つの原子量単位（amu）または1ダルトンとして定義しています。電子は陽子よりもずっと質量が小さく、9.11×10-28グラム、つまり原子量単位の1/1800程度しかありません。そのため、元素の全体的な原子量にはほとんど寄与しません。これはつまり、原子量を考慮する場合、電子の質量を無視して陽子と中性子の数だけに基づいて原子の質量を計算するのが通常です。 しかし、ほとんどの自然発生元素は同位体から構成されているため、そのような元素の原子量を決定する際には同位体の質量と自然存在量を考慮することが重要です。このような場合における原子量は、各同位体の質量を自然的な割合で掛け合わせたものの合計として計算されます。 化学者は化学反応に参加する化合物の原子数を決定するために「モル」という単位をよく使用します。元素のモルは、その原子量（グラム）であり、化合物のモルはその成分の原子量（分子量とも呼ばれる）の合計です。よく使われる例として、化学式C6H12O6のグルコースのモルを計算することがあります。炭素（C）の原子量は12.011グラムであり、グルコースには炭素が6つ含まれているため、合計原子量は72.066グラムです。水素（H）と酸素（O）に対しても同様の計算を行うと、グルコースの分子量は180.156グラムになります。 このテキストは、一部が <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>

陽子と中性子の質量はほぼ同じで、10〜24グラム×約1.67です。科学者たちは、この質量の量を恣意的に1つの原子質量と定義しています...

Education

JoVE Core

Anatomy and Physiology

解剖生理学

Unit 1

ユニット1

Fundamentals of Chemistry

化学の基礎

KEY TERMS AND CONCEPTS

主要用語と概念

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 weight

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key terms and concepts

Learn how protons, neutrons, isotopes, and the mole are used to calculate atomic mass and molecular weight with a glucose example for high school chemistry.

Atomic Mass and Mole Calculations | JoVE K12

anatomy and physiology

JoVE Core 解剖学と生理学では、人体の解剖学的および生理学的な詳細を、包括的で明確で魅力的なビデオ アニメーションで紹介します。このレッスン集は、人体の構造、コンポーネント、機能、要件に焦点を当てています。この知識を実際の医療および研究現場で応用することを実証する科学者による実際のビデオによって補完されています。

Atomic Mass and Mole Calculations

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