Name: atomic elements, molecules, and bonds
Uploaded: 2020-09-03T13:38:25.000Z
Duration: 2 min 38 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.3.3

Molecules and Compounds

כל חומר בטבע מורכב מיחידות כימיות בסיסיות הנקראות יסודות ולהן מאפיינים פיזיקליים וכימיים ייחודיים. הטבלה המחזורית מכילה בסך הכול 118 יסודות שהתגלו עד כה. יחידת הבסיס המרכיבה כל יסוד היא אטום.יסודות מסוימים כמו הליום, ניאון, כסף או פלטינה קיימים כיחידות של אטומים בודדים. יסודות אחרים כמו מימן, חמצן, או גופרית קיימים כיחידות של שני אטומים זהים או יותר. אטומים מרובים אלה מוחזקים יחד על ידי כוחות אלקטרוסטטיים חזקים הנקראים קשרים כימיים, היוצרים יחידות יציבות, הנקראות מולקולות.בנוסף לכך, שני יסודות שונים או יותר יכולים גם ליצור מולקולות כמו מים או פרוקטוז. מולקולות אלה, הנוצרות על ידי שילובים של אטומים של שני יסודות או יותר המחוברים כימית ביחס קבוע, נקראים תרכובות. לכן, מולקולות מים ופרוקטוז הן גם תרכובות.מולקולת מים מורכבת משני אטומים של מימן ואטום אחד של חמצן. לעומת זאת, פרוקטוז היא מולקולה המכילה שישה אטומי פחמן, 12 אטומי מימן ושישה אטומי חמצן. האטומים הבודדים בתוך התרכובת מוחזקים יחד בקשרים כימיים, המכתיבים את התרכובת שנוצרת כמו תרכובת מולקולרית יונית.תרכובות מולקולריות קוולנטיות, כמו מים, נוצרות כאשר אטומי אל-מתכות נפגשים וחולקים את אלקטרוני הערכיות שלהם באמצעות קשר קוולנטי. האלקטרונים המשותפים לשני האטומים מקטינים את האנרגיה הפוטנציאלית ויוצרים מולקולות שהן יציבות יותר מאטומים בודדים. תרכובות יוניות כמו נתרן כלורי נוצרות כשאטומים של מתכת ואל מתכת מתחברים.מתכות גורעות בקלות את האלקטרונים שלהן ונהפכות לקטיוניות בעוד שאל מתכות מקבלות אליהן בקלות אלקטרונים ונהיות אניוניות. וכך בעצם אטומי מתכות מעבירים אלקטרונים לאטומי האל מתכות והאינטראקציות האלקרוסטטיות בין יונים בעלי מטענים הפוכים יוצרים קשרים יוניים. היכולת של יסודות ליצור תרכובות תורמת למגוון הגדול של החומרים הקיימים בטבע.

מולקולות ותרכובות

<div style="direction:rtl"><h4>אטומים ומולקולות</h4> כל דבר ביקום מורכב מחומר, והחומר מורכב משילוב של יסודות. אטום הוא היחידה הקטנה ביותר של יסוד השומרת על כל התכונות של היסוד. לדוגמה, מטבע כסף מורכב מאטומי כסף, וכל אטום כסף שומר על התכונות הייחודיות של היסוד - כסף. יסודות הם חומרים טהורים המורכבים מאטומים זהים שלא ניתן לפרק אותם לחומרים פשוטים יותר על ידי שינויים כימיים. יסודות אטומיים מכילים אטומים בודדים כיחידה הבסיסית שלהם. פחמן מורכב מאטומי פחמן, ונתרן מורכב מאטומי נתרן. רוב היסודות הם יסודות אטומיים. עם זאת, ישנם כמה יסודות הקיימים כשילוב של אטומים, ולעולם לא נמצאים בטבע כאטומים בודדים. אלה נקראים יסודות מולקולריים. יסודות מולקולריים קיימים כמולקולות עם שני אטומים או יותר הקשורים זה לזה. הם יכולים להיות דו-אטומיים, כמו מימן (H2), חמצן (O2), או גז כלור (Cl2), או פוליאטומי, כמו גופרית (S8) וזרחן (P4). מולקולה מורכבת משני אטומים או יותר המחוברים לכוחות חזקים הנקראים קשרים כימיים. מולקולה עשויה להיות מורכבת משני אטומים או יותר זהים, או שהיא עשויה להיות מורכבת משני או יותר אטומים שונים. כאשר המולקולה מורכבת מאטומים משני יסודות שונים או יותר המשולבים ביחסי מספרים שלמים וקבועים, גם המולקולה היא תרכובת. לדוגמה, מים הם תרכובת, וכל מולקולת מים (H2O) היא יחידה המכילה שני אטומי מימן ואטום חמצן אחד. המולקולה גלוקוז (C6H12O6) היא גם תרכובת המכילה שישה אטומי פחמן, שנים עשר אטומי מימן ושישה אטומי חמצן. תרכובות הן חומרים טהורים המורכבים משניים או יותר יסודות בפרופורציות קבועות ומוגדרות. תרכובות מסווגות כמולקולריות או יוניות על סמך הקשרים הקיימים. <h4>תרכובות</h4> טבעם של כוחות המשיכה המחזיקים אטומים יחד בתוך תרכובת קובעת את סוג הקשר הכימי הנוצר. העברה מלאה של אלקטרונים בין אטום מתכת לאטום שאינו מתכתי מביאה ליצירת יונים בעלי מטען הפוך. המשיכה האלקטרוסטטית בין היונים נקראת קשר יוני, והתרכובות הנוצרות באמצעות קשרים יוניים הן תרכובות יוניות. לדוגמה, נתרן כלורי NaCl הוא תרכובת יונית. שיתוף האלקטרונים בין שני אטומים לא מתכתיים או יותר מביא לקשרים קוולנטיים, והתרכובות הנוצרות באמצעות קשרים קוולנטיים נקראות תרכובות קוולנטיות או מולקולריות. קשרים קוולנטיים הם כוחות המשיכה בין הגרעינים הטעונים בחיוב של האטומים המחוברים לבין אלקטרונים בעלי מטען שלילי המשותפים בין האטומים. טקסט זה מותאם מ <a href="https://openstax.org/books/chemistry-2e/pages/2-6-molecular-and-ionic-compounds">OpenStax Chemistry 2e, Section 2.6: Molecular and Ionic Compounds.</a></div>

אטומים ומולקולות

כל דבר ביקום מורכב מחומר, והחומר מורכב משילוב של אלמנטים. אטום הוא היחידה הקטנה ביותר של ...

Education

JoVE Core

כימיה

אחד

Molecules, Compounds, and Chemical Equations

מולקולות, תרכובות ומשוואות כימיות

molecules-compounds-and-chemical-equations

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

atomic elements, molecules, and bonds

Matter is made of elements, and elements are built from atoms. An atom is the smallest unit of an element that still keeps that element’s properties. A silver coin, for example, is made of silver atoms. Each atom keeps the unique properties of silver.

Elements are pure substances made of identical atoms. They cannot be broken down into simpler substances by chemical changes. Most elements are atomic elements, which use single atoms as their basic unit. Carbon and sodium are examples of atomic elements.

Some elements do not occur as single atoms in nature. These are called molecular elements. They exist as molecules made of two or more bonded atoms. Some are diatomic, such as hydrogen (H2), oxygen (O2), and chlorine (Cl2). Others are polyatomic, such as sulfur (S8) and phosphorous (P4).

A molecule is a group of two or more atoms joined by strong chemical bonds. The atoms in a molecule may be the same, or they may be different. When a molecule contains atoms from two or more different elements in fixed whole number ratios, it is also a compound. Water is a compound, and each H2O molecule has two hydrogen atoms and one oxygen atom. Glucose (C6H12O6) is another compound, with six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.

Compounds are pure substances made of two or more elements in fixed, definite proportions. They are classified as molecular or ionic based on the bonds they contain. The kind of attraction between atoms determines the bond type. When electrons transfer completely from a metal atom to a nonmetal atom, oppositely charged ions form. The electrostatic attraction between those ions is an ionic bond, and the result is an ionic compound such as sodium chloride (NaCl). When two or more nonmetal atoms share electrons, they form covalent bonds. Compounds formed this way are covalent, or molecular, compounds.

Atomic Elements, Molecules, and Bonds

molecules and compounds

Matter is made of elements, and elements are built from atoms. An atom is the smallest unit of an element that still keeps that element’s properties. A silver coin, for example, is made of silver atoms. Each atom keeps the unique properties of silver. Elements are pure substances made of identical atoms. They cannot be broken down into simpler substances by chemical changes. Most elements are atomic elements, which use single atoms as their basic unit. Carbon and sodium are examples of atomic...

molecular models

Molecular Model Types in Chemistry

Molecular models help chemists and students visualize the structures and shapes of atoms and molecules. They represent the molecular architecture of chemical compounds in a way that is easier to study than formulas alone. Skeletal models are simple two-dimensional drawings of compounds. They show the molecular framework, or the bonds, without drawing every atom. In this model, many carbon and hydrogen atoms are not shown directly. Their positions are implied by the ends and junctions of the...

organic compounds

Organic Molecules in Everyday Chemistry

Organic molecules are carbon-based compounds found in living things and in many everyday products. Most organic compounds have carbon as the main element, bonded to hydrogen and other carbon atoms. Some carbon-containing substances, such as carbonates, cyanides, and simple oxides like CO and CO2, are not classified as organic. Carbon can form up to four strong bonds, which helps explain why organic compounds can make chains and rings of many sizes and shapes. These molecules appear in...

formula mass and mole concepts of compounds

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Chemical Formula Mass and Percent Composition

Chemical formula mass and percent composition help describe the makeup of compounds. A chemical formula shows which atoms are present and how many of each atom appear in a substance. For covalent compounds, the formula shows the atoms in one molecule. That is why formula mass can also be called molecular mass. Chloroform, CHCl3, is one example. Its formula shows one carbon atom, one hydrogen atom, and three chlorine atoms. The molecular mass is the sum of their average atomic masses. Ionic...

experimental determination of chemical formula

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Finding Empirical and Molecular Formulas

Chemical formulas show the elemental makeup of a compound. When a formula is unknown, scientists often start by measuring the masses of the elements in the sample. Those mass data are then used to find the simplest whole-number ratio of atoms, which gives the empirical formula. To get from mass to atom ratio, the masses of the elements are first converted to moles using molar masses. Chemical formulas describe numbers of atoms, not masses, so this step is necessary. In one example, 1.71 grams...

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Reading Chemical Equations and Balancing Them

Chemical equations show the identities and relative amounts of substances in a chemical reaction. The substances that react are called reactants, and their formulas are written on the left side of the equation. The substances formed are called products, and their formulas are written on the right side. A plus sign (+) separates formulas on the same side, and an arrow (→) shows the change from reactants to products. The numbers in a chemical equation are shown with coefficients. A coefficient...

key terms and concepts

Learn how atoms form elements, molecules, and compounds, and compare ionic and covalent bonds using examples like water, glucose, and sodium chloride.

Atomic Elements, Molecules, and Bonds | JoVE K12

chemistry

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Study Of Matter

Classification of matter

Virginia  Standards of Learning

HIgh School

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Alabama Course of Study Science

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9-12.PS.3.4.c

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Scientific Laws

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Matter: Pure Substances and Mixtures
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The Atomic Theory of Matter

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Subatomic Particles

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Elements: Chemical Symbols and Isotopes

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Use models to explain how the scientific understanding of atomic structure has evolved.

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Radioactivity and Nuclear Equations

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Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10&#8722;15 meters, a nucleus is ...

Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

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Nuclear Transmutation

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Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

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Atomic Orbitals

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The Pauli Exclusion Principle

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The Energies of Atomic Orbitals

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The Aufbau Principle and Hund's Rule

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Periodic Classification of the Elements

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The Periodic Table

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Atomic Mass

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Molar Mass

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Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

PS.Chm.2.2

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Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a ...

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Trends in Lattice Energy: Ion Size and Charge

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Electronegativity

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Bond Polarity

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Lewis Structures of Molecular Compounds and Polyatomic Ions

To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:


	Determine the ...

Resonance

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Formal Charges

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Exceptions to the Octet Rule

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	...

Bond Energies and Bond Lengths

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Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

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Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Intermolecular vs Intramolecular Forces

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Intermolecular Forces

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Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

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surface-tension-capillary-action-and-viscosity

Surface Tension, Capillary Action, and Viscosity

Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded ...

Hydrogen Bonds

Hydrogen BondsHydrogen bonds are weak attractions between atoms that have formed other chemical bonds. One of these atoms is electronegative, like oxygen, ...

Van der Waals Interactions

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Construct an explanation to summarize the influences intermolecular forces have on the properties of chemical compounds.

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Atoms and Molecules

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Molecular Models

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Classification of Elements and Compounds

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Ionic Compounds: Formulas and Nomenclature

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Molecular Compounds: Formulas and Nomenclature

Molecular compounds or covalent compounds result when atoms share electrons to form covalent bonds. Since there is no electron transfer, molecular ...

Use models to predict chemical names and formulas including ionic (binary & ternary), acidic, and binary covalent compounds.

Analyze the structure of atoms and isotopes.

Atomic Elements, Molecules, and Bonds

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