Name: reading molecular, empirical, and structural formulas
Uploaded: 2020-09-03T13:38:26.000Z
Duration: 2 min 52 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

Chemical Formulas

Los compuestos químicos son sustancias que están formadas por dos o más elementos en proporciones específicas. Para describir estos compuestos de manera precisa, se desarrollaron las fórmulas químicas. Una fórmula química brinda información sobre los elementos y el número de iones o átomos involucrados.Los elementos se expresan con su símbolo químico, mientras que el número relativo de iones o átomos se señala con un subíndice. Por ejemplo, el azúcar común o sacarosa es un compuesto que contiene los siguientes elementos:carbono, hidrógeno y oxígeno, que se representan con los símbolos C, H y O.Los números doce, veintidós y once indican el número total de átomos de carbono, hidrógeno y oxígeno que están presentes en este compuesto. En general, los elementos no se organizan por orden alfabético, sino que se comienza con los elementos que tienen una carga más positiva, o elementos metálicos, seguidos por los de carga más negativa, o elementos menos metálicos, como el hidróxido de potasio.Las fórmulas químicas se clasifican en molecular, empírica y estructural. Las fórmulas moleculares describen un compuesto enumerando cada elemento y el número exacto de átomos presentes en el mismo. La fórmula molecular de la glucosa es C6H12O6, es decir, que la glucosa está compuesta por seis átomos de carbono, doce de hidrógeno y seis de oxígeno.La fórmula empírica muestra la proporción más simple de número entero en la que están presentes los átomos de los elementos. En la glucosa, la proporción más simple de átomos de carbono, hidrógeno y oxígeno es 1:2:1, lo que resulta en la fórmula empírica CH2O. La fórmula molecular de un compuesto también es un número entero que es múltiplo de su fórmula empírica.En la glucosa, la multiplicación de la fórmula empírica con el número entero seis da como resultado la fórmula molecular. Por otra parte, la fórmula estructural presenta gráficamente la relación entre los átomos individuales. Los símbolos químicos representan los átomos y las líneas señalan los enlaces químicos.Una sola línea representa un solo enlace, y dos y tres líneas indican enlaces dobles y triples, respectivamente. Los modelos extendidos de la fórmula estructural, como el de proyección de caballete, el de barras y esferas o el de espacio lleno, ofrecen varias perspectivas tridimensionales sobre la forma molecular. De las tres fórmulas químicas, la fórmula estructural brinda la mayor cantidad de información sobre el compuesto químico, seguido por la fórmula molecular.La fórmula empírica es la menos informativa.

fórmulas químicas

Una fórmula química presenta información sobre la proporcion de átomos que constituyen un compuesto químico o molécula particular, utilizando principalmente símbolos de elementos y números. A veces también se utilizan otros símbolos, como guiones, paréntesis, corchetes, comas y los signos más y menos. Una fórmula química puede ser uno de tres tipos– Molecular, empírica y estructural.
 
 <h4>Fórmula molecular</h4>
 
 La fórmula molecular representa una molécula o un compuesto químico utilizando símbolos químicos (para indicar los tipos de átomos) y números de subíndice (para mostrar el número de átomos de cada tipo en la molécula). Las fórmulas moleculares también se utilizan como abreviaturas para los nombres de compuestos.
 
 Algunos elementos consisten en átomos individuales discretos, como los gases nobles helio, neón y argón. Estos elementos se llaman gases monoatómicos y tienen fórmulas moleculares He, Ne y Ar, respectivamente. Pocos elementos existen como moléculas formadas por dos o más átomos químicamente unidos del mismo elemento. Por ejemplo, elementos como el hidrógeno, el oxígeno y el nitrógeno existen como moléculas diatómicas que contienen dos átomos cada uno y, por lo tanto, tienen las fórmulas moleculares H2, O2 y N2, respectivamente. Asimismo, elementos como el fósforo y el azufre existen como moléculas poliatómicas con fórmulas moleculares P4 y S8, respectivamente. 
 
 Es importante señalar que un subíndice que sigue a un símbolo y un número delante de un símbolo no representan lo mismo; por ejemplo, H2 y 2H representan especies claramente diferentes. H2 es una fórmula molecular; representa una molécula diatómica de hidrógeno, que consiste en dos átomos del elemento que están unidos químicamente. La expresión 2H, por otro lado, indica dos átomos de hidrógeno separados que no se combinan como una unidad. La expresión 2H2 representa dos moléculas de hidrógeno diatómico.
 
 <h4>Fórmula empírica</h4>
 
 Los compuestos se forman cuando dos o más elementos se combinan químicamente, dando como resultado la formación de enlaces. Por ejemplo, el hidrógeno y el oxígeno pueden reaccionar para formar agua, y el sodio y el cloro pueden reaccionar para formar cloruro de sodio o sal de mesa. A veces describimos la composición de estos compuestos con una fórmula empírica, que indica los tipos de átomos presentes y la relación de números enteros más simple del número de átomos (o iones) en el compuesto. Por ejemplo, el dióxido de titanio (usado como pigmento en la pintura blanca y en el tipo de bloqueador solar grueso y blanco) tiene una fórmula empírica de TiO2. Esto identifica los elementos titanio (Ti) y oxígeno (O) como los constituyentes del dióxido de titanio e indica la presencia del doble de átomos del elemento oxígeno que los átomos del elemento titanio.
 
 En muchos casos, la fórmula molecular de una sustancia se deriva de una determinación experimental tanto de su fórmula empírica como de su masa molecular (la suma de masas atómicas para todos los átomos que componen la molécula). Por ejemplo, se puede determinar experimentalmente que el benceno contiene dos elementos, carbono (C) e hidrógeno (H), y que por cada átomo de carbono en el benceno hay un átomo de hidrógeno. Por lo tanto, la fórmula empírica es CH. Una determinación experimental de la masa molecular revela que una molécula de benceno contiene seis átomos de carbono y seis átomos de hidrógeno, por lo que la fórmula molecular del benceno es C6H6.
 
 <h4>Fórmula estructural</h4>
 
 La fórmula estructural de un compuesto da la misma información que su fórmula molecular (los tipos y números de átomos en la molécula) pero también muestra cómo los átomos están conectados en la molécula. En otras palabras, la fórmula estructural representa gráficamente la estructura molecular de un compuesto. Muestra la probable disposición de los átomos y cómo están conectados en el espacio tridimensional real, dando más información sobre la geometría molecular. Las líneas se utilizan para representar los enlaces presentes entre los átomos. La fórmula también puede representar los ángulos de enlace aproximados, dando un sentido de la forma de la molécula. 
 
 Este texto está adaptado de <a href="https://openstax.org/books/chemistry-2e/pages/2-4-chemical-formulas">Openstax Química 2e, Sección 2.4: Fórmulas Químicas.</a>

Fórmulas Químicas

Una fórmula química presenta información sobre las proporciones de los átomos que constituyen un compuesto o molécula química en particular, utilizando principalmente símbolos de ...

Education

Educación

Book

Química

Molecules, Compounds, and Chemical Equations

Moléculas, compuestos y ecuaciones químicas

molecules-compounds-and-chemical-equations

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 exist as separate atoms. The noble gases helium, neon, and argon are monatomic gases, so their molecular formulas are He, Ne, and Ar. Other elements form molecules with two or more bonded atoms of the same element. Hydrogen, oxygen, and nitrogen are diatomic and have the formulas H2, O2, and N2. Phosphorus and sulfur are polyatomic and have the formulas P4 and S8.

It is important to tell the difference between a subscript and a number in front of a symbol. H2 means one diatomic hydrogen molecule. The expression 2H means two separate hydrogen atoms. The expression 2H2 means two hydrogen molecules.

An empirical formula shows the types of atoms present and the simplest whole-number ratio of those atoms or ions in a compound. Compounds form when two or more elements chemically combine and make bonds. Water and sodium chloride are common examples of compounds. Titanium dioxide has the empirical formula TiO2, which shows titanium and oxygen and means there are twice as many oxygen atoms as titanium atoms.

In many cases, a molecular formula is found from the empirical formula and the molecular mass. Molecular mass is the sum of the atomic masses of all atoms in a molecule. Benzene is one example. Experiments show that benzene contains carbon and hydrogen in a 1:1 ratio, so its empirical formula is CH. Its molecular mass shows that one molecule contains six carbon atoms and six hydrogen atoms, so its molecular formula is C6H6.

A structural formula gives the same atom count information as a molecular formula, but it also shows how the atoms are connected. It draws the molecular structure in a way that helps show the probable arrangement of atoms in three-dimensional space. Lines represent bonds between atoms. Structural formulas may also show approximate bond angles, which gives a sense of molecular shape.

Reading Molecular, Empirical, and Structural Formulas

reading-molecular-empirical-and-structural-formulas

chemical 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...

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...

classification of elements and compounds

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...

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 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...

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...

scientists in action

Científicos en Acción

key terms

Términos clave

key relationships & equations

Relaciones y ecuaciones clave

chapter exercises

Ejercicios del capítulo

appendices

Apéndices

molecules, compounds, and chemical equations

Learn how molecular, empirical, and structural formulas show atom counts, ratios, and bonds. See examples like H2, TiO2, and C6H6.

Reading Molecular, Empirical, and Structural Formulas | JoVE K12

chemistry

PS.Chm.4.3

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Structure And Properties Of Matter

Representing compounds

Virginia  Standards of Learning

HIgh School

CH.3

CH.3.a

Texas Essential Knowledge and Skills

High School

CHEM.8

CHEM.8.D

Florida Department of Education

Physical Science

SC.912.P.8

SC.912.P.8.7

Georgia Standards of Excellence

SPS2.

Chemical Names and Chemical Formulas

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, ...

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.

Reading Molecular, Empirical, and Structural Formulas

Description

Transcript

Tags

More videos by Standards