Name: atomic vs molecular substances and bonding
Uploaded: 2020-09-03T13:38:26.000Z
Duration: 2 min 54 s
Channel: JoVE

K12 Standards

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NC K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.3.3

Classification of Elements and Compounds

In nature, pure substances exist as either elements or compounds. Depending on the basic unit, elements exist in either atomic or molecular form, while compounds can be subcategorized as either molecular or ionic.
Atomic elements have single atoms as their basic units. Helium, neon, and krypton are examples of monatomic elements that can exist as stable individual atoms.
Molecular elements, on the other hand, contain two or more atoms bonded together, forming a molecule as the basic unit. Diatomic hydrogen with two hydrogen atoms and polyatomic sulfur with eight sulfur atoms are examples of molecular elements.
In comparison to molecular elements, molecular compounds are formed when atoms of two or more nonmetallic elements combine by sharing valence electrons through covalent bonds.&#160;
The combination lowers the overall potential energy of the system, thereby driving the formation of a stable molecule. Hence, the basic units of a molecular compound are discrete molecules composed of constituent atoms.
Ethanol is a molecular compound, which contains basic units of distinct ethanol molecules comprising two carbon, six hydrogen, and one oxygen atoms.
Ionic compounds are formed when atoms of metallic elements combine with atoms of one or more nonmetallic elements. The metal atoms readily lose their valence electrons to form positively charged cations while the non-metal atoms gain electrons forming negatively charged anions.
Strong electrostatic attractions or ionic bonds are formed between the oppositely charged ions, thereby lowering the total energy of the system and driving the assembly of stable, ordered, three-dimensional ionic lattice structures.&#160;
The smallest array of ions that form electrically neutral basic units of an ionic compound&#160;is called the formula unit. Table salt is an ionic compound with a formula unit NaCl containing an alternating three-dimensional array of sodium ions and chloride ions.
However, many ionic compounds are composed of ions that are not singular, like sodium or chloride, but made of multiple covalently bonded atoms with a net negative or positive charge &#8212; called polyatomic ions.&#160;
For instance, sodium acetate is composed of positively charged sodium ions and polyatomic acetate ions carrying a net negative charge.

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 a compound consists of two or more types of atoms held together by a chemical bond. Elements are classified as atomic or molecular based on the nature of their basic units.
Compounds are pure substances composed of two or more elements in fixed, definite proportions. Compounds are classified as ionic or molecular (covalent) based on the bonds present in them.
<h4>Molecular Compounds</h4>
Molecular compounds (or covalent compounds) result when two or more different nonmetal atoms share electrons to form covalent bonds. The basic units of molecular compounds are discrete neutral molecules composed of different constituent atoms. For example, the molecular compound carbon monoxide is composed of CO molecules containing covalently bonded carbon and oxygen atoms. Similarly, methanol contains CH3OH molecules as base units, constituting one carbon atom, one oxygen atom, and four hydrogen atoms, all of which are covalently connected.&nbsp;
Molecular compounds can be identified based on their physical properties. Under normal conditions, molecular compounds often exist as gases, low-boiling liquids, and low-melting solids, although exceptions exist.&nbsp;
<h4>Ionic Compounds</h4>
When an element composed of atoms that readily lose electrons (a metal) reacts with an element composed of atoms that readily gain electrons (a nonmetal), a transfer of electrons usually occurs, producing ions. The compound formed by this transfer is stabilized by the electrostatic attractions (ionic bonds) between the ions of opposite charge present in the compound. For example, when each sodium atom in a sample of sodium metal (group 1) gives up one electron to form a sodium cation, Na+, and each chlorine atom in a sample of chlorine gas (group 17) accepts one electron to form a chloride anion, Cl&minus;, the resulting compound, NaCl, is composed of sodium ions and chloride ions in the ratio of one Na+ ion for each Cl&minus; ion.&nbsp;
A compound that contains ions and is held together by ionic bonds is called an ionic compound. Ionic compounds are solids that typically melt at high temperatures and boil at even higher temperatures. In solid form, an ionic compound is not electrically conductive because its ions are unable to flow. When molten, however, it can conduct electricity because its ions can move freely through the liquid.&nbsp;
In every ionic compound, the total number of positive charges of the cations equals the total number of negative charges of the anions. Thus, ionic compounds are electrically neutral overall, even though they contain positive and negative ions.&nbsp;
Many ionic compounds contain polyatomic ions as the cation, the anion, or both. As with simple ionic compounds, these compounds must also be electrically neutral, so their formulas can be predicted by treating the polyatomic ions as discrete units. We use parentheses in a formula to indicate a group of atoms that behave as a unit. For example, the formula for calcium phosphate, one of the minerals in our bones, is Ca3(PO4)2. This formula indicates that there are three calcium ions (Ca2+) for every two phosphate (PO4)3&minus; groups. The (PO4)3&minus; &nbsp;groups are discrete units, each consisting of one phosphorus atom and four oxygen atoms, and having an overall charge of 3&minus;. The compound is electrically neutral, and its formula shows a total count of three Ca, two P, and eight O atoms.
This text is adapted from <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>

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 ...

Education

JoVE Core

Molecules, Compounds, and Chemical Equations

molecules-compounds-and-chemical-equations

KEY TERMS AND CONCEPTS

atomic vs molecular substances and bonding

Pure substances are made of only one kind of matter. A pure substance can be an element or a compound. An element contains only one type of atom. A compound contains two or more types of atoms joined by a chemical bond.

Elements are classified as atomic or molecular based on their basic units. Compounds are classified as ionic or molecular, also called covalent, based on the bonds they contain. Molecular compounds form when two or more different nonmetal atoms share electrons. Their basic units are separate, neutral molecules made of different atoms.

Carbon monoxide is one example of a molecular compound. Its molecules contain carbon and oxygen atoms joined by covalent bonds. Methanol is another example. Its formula, CH3OH, shows one carbon atom, one oxygen atom, and four hydrogen atoms bonded together in each molecule.

Molecular compounds can often be recognized by their physical properties. Under normal conditions, many are gases, low-boiling liquids, or low-melting solids. There are exceptions, but these patterns are common for molecular substances.

Ionic compounds form when a metal reacts with a nonmetal and electrons are transferred. This transfer creates ions. The compound is held together by ionic bonds, which are electrostatic attractions between oppositely charged ions. For example, sodium loses one electron to form Na+, and chlorine gains one electron to form Cl-. The result is sodium chloride, NaCl, with a one-to-one ratio of sodium ions to chloride ions.

Ionic compounds are solids. They usually melt at high temperatures and boil at even higher temperatures. A solid ionic compound does not conduct electricity because its ions cannot move. When molten, it can conduct electricity because the ions are free to flow. In every ionic compound, the total positive charge equals the total negative charge, so the compound is electrically neutral overall.

Many ionic compounds include polyatomic ions as the cation, the anion, or both. These compounds must also stay electrically neutral, so the formula treats the polyatomic ion as a unit. Parentheses show a group of atoms that behaves as one unit. Calcium phosphate, Ca3(PO4)2, is an example from bone minerals. Its formula shows three calcium ions for every two phosphate groups, and the compound contains three calcium atoms, two phosphorus atoms, and eight oxygen atoms in total.

Atomic vs Molecular Substances and Bonding

atomic-vs-molecular-substances-and-bonding

molecules and compounds

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...

chemical formulas

Reading Molecular, Empirical, and Structural Formulas

Chemical formulas show the types and proportions of atoms in a compound or molecule. They use element symbols and numbers. Some formulas also use dashes, parentheses, brackets, commas, plus signs, and minus signs. A molecular formula shows a molecule or compound with chemical symbols and subscript numbers. The symbols tell which atoms are present, and the subscripts show how many of each atom are in the molecule. Molecular formulas can also serve as short names for compounds. Some elements...

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...

Pure substances are made of only one kind of matter. A pure substance can be an element or a compound. An element contains only one type of atom. A compound contains two or more types of atoms joined by a chemical bond. Elements are classified as atomic or molecular based on their basic units. Compounds are classified as ionic or molecular, also called covalent, based on the bonds they contain. Molecular compounds form when two or more different nonmetal atoms share electrons. Their basic...

ionic compounds: formulas and nomenclature

ionic-compounds-formulas-and-nomenclature

Ionic Charges, Formulas, and Naming Rules

Ionic compounds form when metals transfer electrons to nonmetals and create oppositely charged ions. The electrostatic attraction between the ions, called an ionic bond, holds the compound together. Many nonmetals gain electrons by moving toward the electron count of the next noble gas. Group 17 atoms usually gain one electron and form 1− ions, while group 16 atoms usually gain two electrons and form 2− ions. Oxygen is a clear example. A neutral oxygen atom has 8 protons and 8 electrons. When...

molecular compounds: formulas and nomenclature

molecular-compounds-formulas-and-nomenclature

Naming Covalent Compounds and Acids

Molecular compounds are covalent compounds made when atoms share electrons. Because there is no electron transfer, they do not contain ions. They are made of separate, neutral molecules. Since covalent compounds usually form from nonmetals, the periodic table can help students recognize many of them. In many cases, the positions of the elements can also help predict whether a compound is ionic or covalent, although there are exceptions. Molecular compounds are named differently from ionic...

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

Explore how pure substances are grouped into atomic, molecular, ionic, and covalent forms, with examples like CO, methanol, NaCl, and calcium phosphate.

Atomic vs Molecular Substances and Bonding | JoVE K12

chemistry

JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

PS.Chm.4.3

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Ohio’s Learning Standards and Model Curriculum

Physical Science

Study Of Matter

Classification of matter

Bonding and compounds

Structure And Properties Of Matter

Representing compounds

Virginia  Standards of Learning

HIgh School

CH.3

CH.3.a

CH.3.b

PS.4

PS.4.b

Texas Essential Knowledge and Skills

High School

CHEM.7

CHEM.7.B

CHEM.8

CHEM.8.D

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.6.b

9-12.PS.3.4.c

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

South Carolina College and Career Ready Science Standards

C-PS1-1

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 ...

electron-configuration-of-multielectron-atoms

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 ...

bond-polarity-dipole-moment-and-percent-ionic-character

Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

The absolute value of the difference in electronegativity (&Delta;EN) of two bonded atoms provides a rough measure of the polarity to be ...

lewis-structures-of-molecular-compounds-and-polyatomic-ions

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

molecular-comparison-of-gases-liquids-and-solids

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 ...

comparing-intermolecular-forces-melting-point-boiling-point

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 ...

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

PS.Chm.3.2

Analyze the structure of atoms and isotopes.

Atomic vs Molecular Substances and Bonding

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