Name: how atoms bond to reach stability
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 1 s
Channel: JoVE

קשרים כימיים מחזיקים את האטומים של מולקולה או תרכובת יחד. קשרים נוצרים כאשר האלקטרונים במעטפת הערכיות של האטום נתרמים או משותפים עם אטומים אחרים.
לדוגמה, קשרים יוניים נוצרים כאשר אטומים תורמים או מקבלים אלקטרונים, וממלאים את קליפת הערכיות שלהם. אטום התורם אלקטרונים והופך לבעל מטען חיובי הוא קטיון, ואילו אטום המקבל אלקטרונים והופך לבעל מטען שלילי הוא אניון.
במלח שולחן, הקשר בין קטיון הנתרן לבין אניון הכלוריד הוא קשר יוני.
קשרים קוולנטיים נוצרים בין אטומים החולקים באופן הדדי זוג אחד או יותר של אלקטרונים ערכיים.
לדוגמה, שני אטומי מימן יכולים לחלוק זוג אלקטרונים, וליצור קשר קוולנטי יחיד. חמצן וחנקן יכולים לחלוק שניים ושלושה זוגות אלקטרונים, וליצור קשרים כפולים ומשולשים.

מבוא לקשרים כימיים

Introduction to Chemical Bonds

<div style="direction:rtl">
קשרים כימים

האלקטרונים של רמת האנרגיה החיצונית קובעים את היציבות האנרגטית של האטום ואת נטייתו ליצור קשרים כימיים עם אטומים אחרים. למעטפת האלקטרונים הפנימית ביותר יש קיבולת מקסימלית של שני אלקטרונים, אך לשתי קליפות האלקטרונים הבאות יכולות להיות לכל היותר שמונה אלקטרונים. זה ידוע בתור כלל השמינייה, הקובע כי למעט הקליפה הפנימית ביותר, האטומים הם היציבים ביותר מבחינה אנרגטית כאשר יש להם שמונה אלקטרונים במעטפת הערכיות שלהם, מעטפת האלקטרונים החיצונית ביותר.

עם זאת, מכיוון שלא לכל היסודות יש מספיק אלקטרונים כדי למלא את הקליפות החיצוניות ביותר שלהם, אטומים יוצרים קשרים כימיים עם אטומים אחרים, ובכך מקבלים את האלקטרונים הדרושים להם כדי להשיג תצורה אלקטרונית יציבה. לכן, קשר כימי הוא הכוח שמחזיק אטומים יחד במולקולה או תרכובת.

קשרים יוניים

אטומים יכולים לצבור או לאבד אלקטרונים כדי למלא את מעטפת הערכיות שלהם. בכך, הם נעשים טעונים חשמלית ונקראים יונים. קטיון הוא אטום בעל מטען חיובי שמאבד אלקטרונים, בעוד אטום שצובר אלקטרונים והופך למטען שלילי הוא אניון. המטענים ההפוכים של קטיונים ואניונים מפעילים משיכה הדדית חזקה בינונית השומרת על האטומים בקרבת מקום ויוצרים קשר יוני. קשר יוני הוא קשר מתמשך והדוק בין יונים בעלי מטען הפוך. מלח שולחני רגיל חייב את קיומו לקשר יוני.

קשרים קוולנטיים

דרך נוספת שניתן לספק את כלל האוקטטים היא על ידי שיתוף אלקטרונים בין אטומים ליצירת קשרים קוולנטיים. קשרים אלו חזקים יותר ושכיחים הרבה יותר מקשרים יוניים במולקולות של אורגניזמים חיים. קשרים קוולנטיים נמצאים בדרך כלל במולקולות אורגניות המבוססות על פחמן, כמו ה-DNA והחלבונים שלנו. קשרים קוולנטיים נמצאים גם במולקולות אנאורגניות כמו מים, פחמן דו חמצני וחמצן.

קשרי מימן

קשר מימן נוצר כאשר אטום מימן חיובי חלש שכבר קשור לאטום אלקטרוניטיבי אחד (לדוגמה, החמצן במולקולת המים) נמשך לאטום אלקטרונילי אחר ממולקולה אחרת. הדוגמה הנפוצה ביותר של קשרי מימן בעולם הטבע מתרחשת בין מולקולות מים. זה קורה בכל פעם ששתי טיפות גשם מתמזגות לחרוז גדול יותר או שנחל נשפך לנהר. קשר מימן מתרחש מכיוון שאטום החמצן השלילי החלש במולקולת מים אחת נמשך לאטומי המימן החיוביים החלשים של שתי מולקולות מים אחרות.

טקסט זה מותאם חלקית מ <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/2-2-chemical-bonds?query=chemical%20bond&target=%7B%22type%22%3A%22search% 22%2C%22index%22%3A0%7D#fs-id1493624">Openstax, Anatomy and Physiology 2e, Section 2.2: Chemical Bonds.</a> <a href="https:// openstax.org/books/biology-ap-courses/pages/2-1-atoms-isotopes-ions-and-molecules-the-building-blocks?query=chemical%20bonds">Openstax, Biology for AP® Courses</a> <a href="https://openstax.org/books/biology-ap-courses/pages/2-1-atoms-isotopes-ions-and-molecules-the-building-blocks?query=chemical%20bonds">Section2.1 Atoms, Isotopes, Ions, and Molecules: The Building Blocks.</a>
</div>

קשרים כימיים
האלקטרונים של רמת האנרגיה החיצונית ביותר קובעים את היציבות האנרגטית של האטום ואת נטייתו ליצור קשרים כימיים עם ...

Education

JoVE Core

Anatomy and Physiology

אנטומיה ופיזיולוגיה

Unit 1

יחידה 1

Fundamentals of Chemistry

יסודות הכימיה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

how atoms bond to reach stability

Atoms bond to become more stable, and their outermost electrons play the biggest role in that process. The inner electron shell can hold two electrons. The next two shells can each hold eight electrons. This is called the octet rule. It states that, except for the innermost shell, atoms are most stable when their valence shell, or outer shell, has eight electrons.

When atoms do not have enough electrons to fill that outer shell, they form chemical bonds with other atoms. A chemical bond is the force that holds atoms together in a molecule or compound. These bonds let atoms reach a more stable electron arrangement.

One common type is an ionic bond. In this case, atoms gain or lose electrons to fill their valence shell. When they do this, they become ions. A cation is a positively charged ion that has lost electrons. An anion is a negatively charged ion that has gained electrons. The opposite charges attract each other and keep the ions close together. This close association forms an ionic bond. Table salt is a common example of a substance made through ionic bonding.

Another way atoms satisfy the octet rule is by sharing electrons. This creates covalent bonds. Covalent bonds are stronger and much more common than ionic bonds in the molecules of living organisms. They are found in carbon-based organic molecules such as DNA and proteins. They also occur in inorganic molecules like water, carbon dioxide, and oxygen.

Hydrogen bonds are a weaker kind of attraction. They form when a weakly positive hydrogen atom, already bonded to another electronegative atom such as oxygen, is attracted to a different electronegative atom in another molecule. Water is the most common example. Hydrogen bonding helps explain why raindrops can merge into larger beads and why a creek can flow into a river.

How Atoms Bond to Reach Stability

what is matter?

Matter, Mass, and Weight Basics

Matter is the substance that makes up the universe, from a grain of sand to a star. Scientists define matter as anything that occupies space and has mass. Mass is the amount of matter in an object, while weight depends on gravity. Mass stays the same whether an object is on Earth or in the zero-gravity environment of outer space. Weight changes when gravity changes. An object weighs more where gravity is stronger and less where gravity is weaker. A piece of cheese that weighs a pound on Earth...

the periodic table and organismal elements

the-periodic-table-and-organismal-elements

Organismal Elements in the Periodic Table

The periodic table helps identify the elements that make up living organisms. Biology groups these as organismal elements because they are the chemical building blocks of life. These elements are found in different amounts in the body. Some are present in large quantities, while others are needed only in small amounts. The video connects the periodic table to the elements that organisms actually use. Understanding organismal elements helps students link chemistry to biology. It shows how...

atomic structure

From Atomos to the Modern Atom

Atoms are the tiny building blocks of matter, and ideas about them go back to the Greek philosopher Democritus. He suggested that everything on Earth is made of atomos, a Greek word meaning "indivisible." That idea later led to the modern word atom. In the 19th century, John Dalton developed an atomic theory that is still largely correct today. He proposed five key ideas. All matter is made of tiny particles called atoms. Atoms of the same element are alike, and atoms of different elements are...

chemical symbols

Chemical Symbols and Element Names

Chemical symbols are short abbreviations that stand for an element or a single atom of that element. Mercury, for example, has the symbol Hg. The same symbol can point to one atom of mercury in the microscopic domain or to a sample labeled as many atoms of mercury in the macroscopic domain. Many symbols come from the element’s common name. Others are shortened from a name in another language. Most chemical symbols use one or two letters. For a few elements with atomic numbers above 112,...

atomic number and mass number

Atomic Identity, Mass, and Isotopes

Atomic identity depends on the number of protons in the nucleus, and mass depends on protons and neutrons together. The number of protons is the atomic number, or Z. It defines the element. For example, any atom with six protons is carbon, no matter how many neutrons or electrons it has. In a neutral atom, the number of protons equals the number of electrons. Because of that, the atomic number also tells you the number of electrons in the atom. The total number of protons and neutrons is...

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,...

isotopes and radioisotopes

Radioisotopes in Medicine and Imaging

Radioisotopes are unstable isotopes that can be used to study the body and treat disease. An isotope is an atom of the same element that has a different mass because it contains a different number of neutrons. It still has the same number of protons, so it remains chemically identical. English chemist Frederick Soddy explained this idea in the early 1900s and later received the Nobel Prize in Chemistry in 1921. Some isotopes have more neutrons than usual and are called heavy isotopes. These...

electron behavior

Electron Shells and Discovery

Electrons are negatively charged subatomic particles that stay near the positively charged nucleus of an atom. They occupy spaces linked to energy levels called shells. They are also arranged into subshells and orbitals within each shell. An electron’s shell shows its general energy level. Electrons closer to the nucleus have less energy, while electrons farther away have more energy. The outer shells have more space, so they can hold more electrons than the inner shells. Subshells describe...

introduction to chemical bonds

Atoms bond to become more stable, and their outermost electrons play the biggest role in that process. The inner electron shell can hold two electrons. The next two shells can each hold eight electrons. This is called the octet rule. It states that, except for the innermost shell, atoms are most stable when their valence shell, or outer shell, has eight electrons. When atoms do not have enough electrons to fill that outer shell, they form chemical bonds with other atoms. A chemical bond is the...

ionic bonds

Ionic Bonds and Charge Transfer

Ionic bonds form when atoms transfer electrons and become charged particles. A positive ion and a negative ion attract each other because opposite charges pull together. This type of bonding helps explain how some substances are held together. In many cases, an atom loses one or more electrons, while another atom gains them. The atom that loses electrons becomes a cation, which is a positively charged ion. The atom that gains electrons becomes an anion, which is a negatively charged ion. The...

covalent bonds

Polar and Nonpolar Covalent Bonds

Covalent bonds form when atoms share electrons to fill their valence shells. The way those shared electrons are pulled depends on electronegativity, which is an atom's tendency to attract electrons in a bond. That difference also helps explain why some molecules are polar and others are nonpolar. Atoms with similar electronegativities form nonpolar covalent bonds. In these bonds, electrons are shared equally, so there is no charge across the molecule. When two atoms have different...

hydrogen bonds

Hydrogen Bonding and DNA Stability

Hydrogen bonding helps explain why some molecules stick together more strongly than others. A hydrogen bond forms when a weakly positive hydrogen atom, already bonded to an electronegative atom, is attracted to another electronegative atom on a nearby polar molecule. Common examples include water, hydrogen fluoride, and ammonia. This attraction happens because hydrogen has a much lower electronegativity than atoms such as fluorine, oxygen, and nitrogen. The electronegativity difference, along...

ions, molecules, and compounds

Atomic Charges, Bonds, and Compounds

Atoms can gain or lose electrons during chemical reactions and become ions. An ion is an atom with an electrical charge. This charge is positive or negative, and it often helps the atom reach a full valence shell. Some atoms are more likely to donate electrons, while others are more likely to accept them. Potassium is one example. It has atomic number 19 and one electron in its valence shell, so it is likely to donate that electron and become a slightly positive ion called a cation. Fluorine...

states of matter

Solids, Liquids, Gases, and Plasma

Solids, liquids, gases, and plasma are the main forms of matter described here. Solids are rigid and keep a definite shape. Liquids flow and take the shape of their container, although gravity gives the surface a flat or slightly curved top. Solids and liquids also have volumes that stay nearly the same even when pressure changes. Gases behave differently from solids and liquids. A gas takes both the shape and the volume of its container. In matter with this behavior, the particles are far...

colloids and suspensions

Suspensions, Sedimentation, and Colloids

Suspensions and colloids are two common kinds of mixtures seen in everyday life. Mud and water, flour and water, and tempera paint are suspensions. These mixtures are heterogeneous, which means their particles are not spread out evenly. The particles are relatively large and can be seen with the naked eye or a magnifying glass. Suspension particles make mixtures cloudy, and they settle out after mixing. The settling of particles in a suspension is called sedimentation. A blood test can measure...

introduction to chemical reactions

Chemical Reaction Basics and Equilibrium

Chemical reactions start with reactants and end with products. Reactants are the substances that enter a reaction, and products are the new substances that form. For example, sodium and chloride ions are the reactants in the formation of table salt. Chemical reactions follow the law of conservation of mass. Matter is not created or destroyed during the reaction. That means the atoms and elements in the reactants are still present in the products, and nothing new appears in the products that...

types of chemical reactions: anabolic and catabolic

types-of-chemical-reactions-anabolic-and-catabolic

Anabolism, Catabolism, and ATP Use

Anabolism and catabolism are the two main kinds of metabolic reactions in the body. Metabolism is the total set of anabolic and catabolic reactions that keep life running. These reactions follow the first law of thermodynamics, which says energy cannot be created or destroyed. It can only change form. Anabolism builds larger, more complex molecules from smaller ones. These anabolic, or biosynthesis, reactions need energy in the form of ATP. They join monosaccharides into polysaccharides, fatty...

types of chemical reactions: exchange and reversible

types-of-chemical-reactions-exchange-and-reversible

Electron Transfer and Chemical Equilibrium

Exchange reactions and reversible reactions are two important ideas in chemistry. In an exchange reaction, synthesis and decomposition happen at the same time. Chemical bonds are both formed and broken. These reactions can absorb chemical energy, store it, and release it. A special type of exchange reaction is the oxidation-reduction reaction, or redox reaction. In a redox reaction, electrons move from one compound to another. The electrons often come from hydrogen atoms, which contain one...

energy transfer in chemical reactions

Chemical Energy and Reaction Types

Chemical reactions depend on energy transfer, chemical bonds, and the way matter collides. A reaction needs enough energy for particles to meet with the right force and precision. That energy can break old bonds and help form new ones. Kinetic energy is the energy of motion. A person lifting a brick uses kinetic energy to move the brick into place on a wall. Once the wall is built, it stores potential energy, which is the energy of position or structure. If the wall falls, that stored energy...

factors influencing the rate of chemical reactions

factors-influencing-the-rate-of-chemical-reactions

Chemical Reaction Rates and Catalysts

Chemical reaction rates depend on how often particles collide and whether those collisions have enough energy to start a reaction. That starting energy is called activation energy. Factors that affect reaction rate either lower that energy or make successful collisions more likely. Concentration and pressure can speed reactions up because they put more particles in the same space. When more particles are present, they are more likely to bump into one another. Chemists can also increase...

acids, bases and neutralization reactions

How pH Affects Cells and Digestion

Acids, bases, and pH help control how cells and body systems work. In biology, pH can strongly affect enzymes, proteins, and nucleic acids. Enzymes work best within a certain pH range, and pH changes can alter their structure or denature them, which changes how they function. Acids release hydrogen ions, or H+, in solution. A hydrogen ion is a proton, so it is very reactive in chemical reactions. Strong acids release all of their H+ in water and ionize completely. Hydrochloric acid (HCl) is a...

key terms and concepts

Learn how atoms use ionic, covalent, and hydrogen bonds to reach stability. Explore valence electrons, ions, and examples like salt and water.

How Atoms Bond to Reach Stability | JoVE K12

anatomy and physiology

JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

How Atoms Bond to Reach Stability

Description

Transcript