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

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.3.3

Molecules and Compounds

In natura, tutta la materia è composta da unità chimiche di base, chiamate elementi, aventi proprietà fisiche e chimiche specifiche. La tavola periodica elenca un totale di 118 elementi identificati fino ad oggi. L'unità costituente di ogni elemento è l'atomo.

Alcuni elementi come l'elio, il neon, l'argento o il platino esistono come unità di singoli atomi indipendenti. Altri elementi come l'idrogeno, l'ossigeno o lo zolfo esistono come unità di due o più atomi identici. Questi atomi sono tenuti insieme da possenti forze elettrostatiche denominate legami chimici, formando unità stabili chiamate molecole.

Inoltre, due o più elementi diversi possono anche combinarsi per formare molecole come l'acqua o il fruttosio. Tali molecole, che sono formate dalla combinazione di atomi di due o più elementi uniti chimicamente in una proporzione fissa, sono anche chiamate composti. Dunque, anche le molecole di acqua e fruttosio sono composti.

L'acqua è una molecola formata da due atomi di idrogeno e un atomo di ossigeno. Al contrario, il fruttosio è una molecola che contiene sei atomi di carbonio, dodici atomi di idrogeno e sei atomi di ossigeno. I singoli atomi all'interno di un composto sono tenuti insieme da legami chimici, che determinano il tipo di composto formato, come un composto ionico o molecolare.

I composti molecolari covalenti, come l'acqua, si formano quando atomi non metallici si uniscono e condividono i loro elettroni di valenza tramite un legame covalente. Gli elettroni condivisi fra due atomi abbassano l'energia potenziale e creano molecole più stabili rispetto ai singoli atomi. I composti ionici, come il cloruro di sodio, si formano quando atomi metallici e non metallici si uniscono.

I metalli perdono facilmente elettroni diventando cationi, mentre i non metalli guadagnano facilmente elettroni diventando anioni. Così gli atomi di metallo trasferiscono gli elettroni ad atomi non metallici e le interazioni elettrostatiche fra gli ioni carichi in modo opposto formano legami ionici. La capacità degli elementi di formare composti contribuisce alla grande diversità della materia che esiste in natura.

molecole e composti

Atomi e molecole

Tutto nell'universo è costituito da materia ed essa è composta da una combinazione di elementi. Un atomo è l'unità più piccola di un elemento che conserva tutte le proprietà dell'elemento. Ad esempio, una moneta d'argento è composta da atomi d'argento e ogni atomo d'argento conserva le proprietà uniche dell'elemento argento.

Gli elementi sono sostanze pure costituite da atomi identici che non possono essere scomposti in sostanze più semplici mediante cambiamenti chimici. Gli elementi atomici contengono singoli atomi come unità di base. Il carbonio è composto da atomi di carbonio e il sodio è composto da atomi di sodio. Molti degli elementi sono elementi atomici. Ci sono, tuttavia, alcuni elementi che esistono come combinazione di atomi e non si trovano mai in natura come atomi singoli. Questi sono chiamati elementi molecolari. Gli elementi molecolari esistono come molecole con due o più atomi legati insieme. Possono essere biatomici, come l'idrogeno (H_2), l'ossigeno (O_2) o il cloro (Cl_2), oppure poliatomici, come lo zolfo (S_8) e il fosforo (P_4).

Una molecola è costituita da due o più atomi uniti da forze forti chiamate legami chimici. Una molecola può essere costituita da due o più atomi identici oppure può essere costituita da due o più atomi diversi. Quando la molecola è costituita da atomi di due o più elementi diversi combinati in rapporti numerici interi fissi, anch’essa è un composto. Ad esempio, l'acqua è un composto e ciascuna molecola d'acqua (H_2O) è un'unità che contiene 2 atomi di idrogeno e 1 atomo di ossigeno. Anche la molecola di glucosio (C_6H_12O_6) è un composto che contiene 6 atomi di carbonio, 12 atomi di idrogeno e 6 atomi di ossigeno.

I composti sono sostanze pure formate da due o più elementi in proporzioni fisse e definite. I composti sono classificati come molecolari o ionici in base ai legami presenti.

Composti

La natura delle forze attrattive che tengono insieme gli atomi all’interno di un composto determina il tipo di legame chimico che si forma. Il trasferimento completo di elettroni tra un atomo metallico e un atomo non metallico determina la formazione di ioni con carica opposta. L'attrazione elettrostatica tra gli ioni è chiamata legame ionico e i composti formati attraverso questi legami sono composti ionici. Ad esempio, il cloruro di sodio NaCl è un composto ionico.

La condivisione di elettroni tra due o più atomi non metallici dà luogo a legami covalenti e i composti formati attraverso i legami covalenti sono chiamati composti covalenti o molecolari. I legami covalenti sono le forze attrattive tra i nuclei carichi positivamente degli atomi legati e gli elettroni carichi negativamente condivisi tra gli atomi.

Questo testo è adattato da <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>

Molecole e composti

Atomi e molecole

Tutto nell'universo è costituito da materia e la materia è composta da una combinazione di elementi. Un atomo è l'unità più piccola di ...

Education

Didattica

JoVE Core

Chimica

Molecules, Compounds, and Chemical Equations

Molecole, composti ed equazioni chimiche

molecules-compounds-and-chemical-equations

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

formula-mass-and-mole-concepts-of-compounds

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

experimental-determination-of-chemical-formula

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...

chemical equations

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

JoVE Core: Chimica illustra concetti chiave di chimica attraverso video animazioni concise e di immediata comprensione. Inoltre, i video della sezione "scienziati in azione" mostrano procedure metodologiche realizzate da ricercatori provenienti dai migliori laboratori internazionali.

PS.Chm.4.3

Physical Science

PS.PSc.1.1

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Study Of Matter

Classification of matter

Virginia  Standards of Learning

HIgh School

CH.3

CH.3.a

Alabama Course of Study Science

Matter and Its Interactions

9-12.PS.3.4.c

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

High School

C-PS1-3.

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Motion and Stability: Forces and Interactions

C-PS2-6.

Scientific Laws and Theories

Scientific Laws

In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. ...

The Scientific Method

Chemistry is an empirical science. Scientists often pose questions to understand the chemistry in everyday life and seek answers to these questions. To ...

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

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

PS.Chm.1.1

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

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

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

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

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

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Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

PS.Chm.2.1

atomic-radii-and-effective-nuclear-charge

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

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

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 ...

trends-in-lattice-energy-ion-size-and-charge

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

Whether a bond is nonpolar or polar covalent is determined by a property of the bonding atoms called electronegativity.&#xA0;

Electronegativity values of ...

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Bond Polarity, Dipole Moment, and Percent Ionic Character

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

The Lewis structure of a nitrite anion (NO2&minus;) may actually be drawn in two different ways, distinguished by the locations of the N-O and N=O ...

Formal Charges

In some cases, there are seemingly more than one valid Lewis structures for molecules and polyatomic ions. The concept of formal charges can be used to ...

Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:


	...

Bond Energies and Bond Lengths

Stable molecules exist because covalent bonds hold the atoms together. The strength of a covalent bond is measured by the energy required to break it, ...

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

PS.Chm.3.1

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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

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions ...

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

Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

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

Atoms and molecules interact with each other through intermolecular forces. These electrostatic forces arise from attractive or repulsive interactions ...

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

PS.Chm.3.2

Atoms and Molecules

Everything in the universe is made up of matter, and matter is composed of a combination of elements. An atom is the smallest unit of ...

Chemical Formulas

A chemical formula presents information about the proportions of atoms constituting a particular chemical compound or molecule, mainly using symbols of ...

Molecular Models

Physical models representing molecular architectures of chemical compounds play essential roles in understanding chemistry. The use of molecular models ...

Classification of Elements and Compounds

Pure substances consist of only one type of matter. A pure substance can be an element or a compound. An element consists of only one type of atom, while ...

ionic-compounds-formulas-and-nomenclature

Ionic Compounds: Formulas and Nomenclature

An element composed of atoms that readily lose electrons (a metal) can react with an element composed of atoms that readily gain electrons (a nonmetal) to ...

molecular-compounds-formulas-and-nomenclature

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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