Name: how valence electrons shape the periodic table
Uploaded: 2020-09-03T13:38:28.000Z
Duration: 4 min
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.2.1

Periodic Classification of the Elements

Los electrones que ocupan la capa más externa de un átomo son los electrones de valencia, mientras que los electrones que ocupan los niveles principales de energía internos son los electrones centrales. Un átomo de sodio con una configuración electrónica 3s1 tiene tres niveles de energía principales. Los niveles de energía principales internos completos con 2s22p6 indican que hay diez electrones centrales seguidos por el tercer nivel más externo que contiene el electrón restante.Por lo tanto, el sodio tiene un electrón de valencia. Del mismo modo, el cloro tiene diez electrones centrales y siete electrones de valencia. Los electrones de valencia son los más alejados del núcleo y se sostienen de forma más suelta.Por lo tanto, son los más fáciles de perder o compartir y juegan un papel importante en la unión química. Los elementos que tienen el mismo número de electrones de valencia exhiben propiedades químicas similares, como se puede ver en la disposición en la tabla periódica moderna. Para los elementos del grupo principal, el número de grupo con letras es igual al número de electrones de valencia y el número de fila es igual al número de quantum principal más alto de ese elemento.Cada elemento de un grupo tiene la misma cantidad de electrones disponibles para el enlace. Abajo del grupo, el número cuántico principal aumenta en uno, mientras que el número de electrones de valencia sigue siendo el mismo. Las dos columnas del extremo izquierdo de la tabla periódica constituyen el bloque s.Para estos elementos, el último electrón entra en un orbital s. Los ementos del grupo uno excepto el hidrógeno se denominan metales alcalinos y son extremadamente reactivos ya que tienen un solo electrón de valencia. Los elementos del grupo dos son los metales alcalinotérreos con dos electrones en la capa de valencia.Las seis columnas de la extrema derecha forman el bloque p. La capa de valencia de estos elementos ha ocupado completamente los orbitales s y el último electrón entra en el orbital p. Del grupo tres A al grupo ocho A, el número de electrones en los orbitales p aumenta en uno.Los gases nobles tienen ocho electrones de valencia excepto el helio, que pertenece al bloque s, y solo tiene dos electrones. El bloque d consta de diez columnas colocadas entre el bloque s y el bloque p. Estos elementos se conocen como metales de transición.El último electrón entra en el orbital d de la capa principal número uno menos el número de fila. En la cuarta fila, tres orbitales la completan, en la quinta fila, cuatro orbitales d, y así sucesivamente. Los elementos de transición internos constituyen el bloque f y hacen que el último electrón entre en un orbital f.El número cuántico principal de los orbitales f que se llenan en cada fila es dos menos que el número de fila. En la sexta fila, los cuatro orbitales f se llenan, y en la séptima fila, se llenan los cinco orbitales f. Los elementos de transición internos están dispuestos en la serie de lantánidos y la serie de actínidos.El número de columnas en cada bloque indica cuántos electrones se pueden llenar en el subnivel del bloque. Dos columnas en el bloque s se correlacionan con un orbital s con dos electrones, seis columnas en el bloque p que representan tres orbitales p con seis electrones, mientras que diez columnas en el bloque d corresponden a cinco orbitales d con dos electrones cada uno. Por último, el bloque f consta de catorce columnas indicando la capacidad máxima de siete orbitales f.

clasificación periódica de los elementos

La tabla periódica organiza los átomos basándose en el número atómico creciente de forma que los elementos con las mismas propiedades químicas se repitan periódicamente. Cuando sus configuraciones electrónicas son añadidas a la tabla, se observa una recurrencia periódica de configuraciones electrónicas similares en las capas externas de estos elementos. Debido a que se encuentran en las capas externas de un átomo, los electrones de valencia juegan el papel más importante en las reacciones químicas. Los electrones externos son los electrones de mayor energía en un átomo y se pierden o comparten con más facilidad que los electrones centrales. Los electrones de valencia son también el factor determinante en algunas propiedades físicas de los elementos.
 
 Las filas horizontales se conocen como períodos. A lo largo de un período, cada elemento consecutivo tiene un protón adicional en el núcleo y un electrón adicional en la capa de valencia. Las columnas verticales son grupos. Los elementos de un grupo (o columna) tienen el mismo número de electrones de valencia (Figura 1); los metales alcalinos litio y sodio tienen cada uno un solo electrón de valencia, los metales alcalinos berilio y magnesio tienen cada uno dos, y los halógenos flúor y cloro tienen siete electrones de valencia.  Es la pérdida, ganancia o compartición de electrones de valencia lo que define cómo reaccionan los elementos. La similitud en las propiedades químicas entre elementos del mismo grupo ocurre porque tienen el mismo número de electrones de valencia. 
 
 Es importante recordar que la tabla periódica fue desarrollada sobre la base del comportamiento químico de los elementos, mucho antes de que cualquier idea de su estructura atómica estuviera disponible. Ahora se entiende la disposición de la tabla periódica; los elementos cuyos átomos tienen el mismo número de electrones de valencia están en el mismo grupo. Las secciones coloreadas de la Figura 1 muestran las tres categorías de elementos clasificados por los orbitales que se están llenando.
 
 <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/1046/1046Image_1v2.png" /> 
 Figura 1: Esta versión de la tabla periódica muestra la configuración de cada elemento. Tenga en cuenta que, en cada grupo, la configuración suele ser similar.
 
 Los elementos del grupo principal se denominan a veces elementos representativos. Estos son los elementos en los que el último electrón agregado entra en un orbital s o p en la capa más externa, que se muestra en azul y rojo en la Figura 1. Esta categoría incluye todos los elementos no metálicos, así como los metaloides y muchos metales. Los electrones de valencia para los elementos del grupo principal son aquellos con el nivel n más alto. Por ejemplo, el galio (GA, número atómico 31) tiene la configuración de electrones [Ar]4s23d104p1, que contiene tres electrones de valencia (subrayados). Los orbitales d completamente llenos cuentan como electrones centrales, no como de valencia.
 
 Las dos columnas del extremo izquierdo comprenden el bloque s y las seis columnas del extremo derecho constituyen el bloque p. Los gases nobles, que forman parte del bloque p, tienen ocho electrones de valencia, excepto el helio que tiene dos. Estos elementos son muy estables y no reactivos.
 
 Elementos de transición o metales de transición: Son elementos metálicos en los que el último electrón agregado entra en un orbital d. Los electrones de valencia en estos elementos (aquellos agregados después de la última configuración de gas noble) incluyen los electrones ns y (n – 1) d. La definición oficial de la IUPAC de los elementos de transición especifica aquellos con orbitales d parcialmente llenos. Así, los elementos con orbitales completamente llenos (Zn, Cd, Hg, así como Cu, Ag, y Au en la Figura 1) técnicamente no son elementos de transición. Sin embargo, el término se utiliza con frecuencia para referirse a todo el bloque d (de color amarillo en la Figura 1).
 
 El bloque d consta de 10 columnas. El número cuántico principal de los orbitales d que se llenan a lo largo de cada fila es igual al número de fila menos uno. En la cuarta fila, se llenan los orbitales 3d</em, en la quinta fila, se llenan los orbitales 4dy así sucesivamente.
 
 Elementos de transición interna: Se muestran en verde en la Figura 1. Las capas de valencia de los elementos de transición interna consisten en las subcapas (n – 2)f, la (n – 1)d y las subcapas ns. Los elementos de transición interna constituyen el bloque f ya que el último electrón entra en un orbital f. El número cuántico principal de los orbitales f que se llenan a lo largo de cada fila es igual al número de fila menos dos. En la sexta fila, se llenan los orbitales 4f, y en la séptima fila, se llenan los orbitales 5f. Hay dos series de transición interna:
 
 <ol>
 <li>La serie lantánida: Lantánido (La) a través del lutecio (Lu)</li>
 <li>La serie actínida: Actínido (Ac) a través del lawrencium (Lr)</li>
 </ol>
 
 Debido a sus similitudes con los otros miembros de la serie, el lantano y el actinio son incluidos y se usan para nombrar la serie a pesar de ser metales de transición sin electrones f.
 
 Este texto es adaptado de <a href="https://openstax.org/books/chemistry-2e/pages/6-4-electronic-structure-of-atoms-electron-configurations">Openstax, Química 2e, Sección 6.4: Estructura Electrónica de los Átomos.</a>

Clasificación Periódica de los Elementos

La tabla periódica organiza los átomos en función del aumento del número atómico para que los elementos con las mismas propiedades químicas se repitan periódicamente. Cuando su ...

Education

Educación

JoVE Core

Química

Periodic Properties of the Elements

Propiedades periódicas de los elementos

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

how valence electrons shape the periodic table

The periodic table organizes elements by increasing atomic number, and it also shows why elements in the same group behave alike. As the electron configurations are placed into the table, a repeating pattern appears in the outer shells of atoms. These outer electrons are called valence electrons, and they play the biggest role in chemical reactions. They are the highest-energy electrons in an atom, so they are easier to lose or share than core electrons. Valence electrons also help determine some physical properties of elements.

The horizontal rows on the periodic table are periods. Moving across a period, each next element has one more proton in the nucleus and one more electron in the valence shell. The vertical columns are groups. Elements in the same group have the same number of valence electrons, which is why they often show similar chemical behavior. For example, lithium and sodium each have one valence electron, beryllium and magnesium each have two, and fluorine and chlorine each have seven. Because elements react by losing, gaining, or sharing valence electrons, their group placement helps predict how they will behave.

It is important to remember that the periodic table was built from chemical behavior before atomic structure was understood. Today, the pattern makes sense because elements with the same number of valence electrons are placed in the same group. The colored regions of the table also show three categories based on which orbitals are being filled. Main group elements, also called representative elements, are the elements whose last added electron enters an s or p orbital in the outermost shell. This category includes all nonmetals, the metalloids, and many metals. For main group elements, the valence electrons are the electrons with the highest n level. Gallium, for example, has the electron configuration [Ar] 4s2 3d10 4p1, so it has three valence electrons. The filled d orbitals are counted as core electrons, not valence electrons.

The two far-left columns form the s-block, and the six far-right columns form the p-block. The noble gases are part of the p-block. They usually have eight valence electrons, except helium, which has two. This helps explain why noble gases are highly stable and unreactive. Transition elements, or transition metals, are metallic elements whose last added electron enters a d orbital. Their valence electrons include the ns and (n - 1)d electrons added after the last noble gas configuration. By the official IUPAC definition, transition elements have partially filled d orbitals, so Zn, Cd, Hg, and also Cu, Ag, and Au are not technically transition elements, even though the term is often used for the whole d-block.

The d-block has 10 columns. As you move across each row, the d orbitals that fill have a principal quantum number that is one less than the row number. In the fourth row, 3d orbitals fill; in the fifth row, 4d orbitals fill; and so on. Inner transition elements form the f-block, where the last electron added enters an f orbital. Their valence shells include the (n - 2)f, the (n - 1)d, and the ns subshells. The f orbitals that fill across each row have a principal quantum number that is two less than the row number. In the sixth row, 4f orbitals fill, and in the seventh row, 5f orbitals fill. The two inner transition series are the lanthanides, from lanthanum through lutetium, and the actinides, from actinium through lawrencium. Lanthanum and actinium are included in those series because they are similar to the other members, even though they are transition metals with no f electrons.

How Valence Electrons Shape the Periodic Table

how-valence-electrons-shape-the-periodic-table

periodic classification of the elements

The periodic table organizes elements by increasing atomic number, and it also shows why elements in the same group behave alike. As the electron configurations are placed into the table, a repeating pattern appears in the outer shells of atoms. These outer electrons are called valence electrons, and they play the biggest role in chemical reactions. They are the highest-energy electrons in an atom, so they are easier to lose or share than core electrons. Valence electrons also help determine...

ionization energy

Ionization Energy Trends in the Periodic Table

Ionization energy is the energy needed to remove an electron from a gaseous atom or ion in its ground state. The first ionization energy, or IE1, removes the most loosely bound electron and forms a 1+ cation. The second ionization energy, IE2, removes the next electron, and each later ionization energy removes another electron from the atom or ion. Ionization always requires energy, so these processes are endothermic. That means ionization energy values are always positive. In general, larger...

atomic radii and effective nuclear charge

atomic-radii-and-effective-nuclear-charge

Periodic Trends in Atomic Size

Periodic trends in atomic size help explain why atoms get larger or smaller across the periodic table. Elements in the same group show similar chemical behavior because they have the same number and arrangement of valence electrons. Across a period, each new element adds one proton to the nucleus and one electron to the valence shell. Down a group, the number of valence electrons stays the same, but the principal quantum number increases by one. Atomic radius is not easy to define with perfect...

ionic radii

How Ionic Charge Changes Ion Size

Ionic radius describes the size of an ion. It changes when an atom gains or loses electrons. Cations are positive ions with fewer electrons than the parent atom, and they are smaller than the atoms they come from. Aluminum shows this pattern clearly. A neutral aluminum atom has a covalent radius of 118 pm, while Al3+ has an ionic radius of 68 pm. When electrons are removed from the outer valence shell, the remaining core electrons feel a stronger effective nuclear charge, or Zeff. That pull...

electron affinity

Electron Affinity Trends on the Periodic Table

Electron affinity is the energy change that happens when a gaseous atom gains an electron and becomes a negative ion, or anion. For many elements, this process releases energy, so the electron affinity value is negative. For some elements, energy must be added instead, so the value is positive. Electron affinity also applies when more than one electron is added. The second electron affinity is the energy change for adding an electron to an anion to make a 2− ion. Later electron affinities...

alkali metals

Alkali Metals: Reactivity Trends

Alkali metals are Group 1 elements with one valence electron. They are soft, shiny metallic solids that are malleable, ductile, and good conductors of heat and electricity. Their melting points are unusually low for metals and drop as you move down the group. Density generally increases down the group, except for potassium. The trend in atomic size helps explain their behavior. Moving from lithium to cesium, each element has a higher principal quantum number, so the outer electron is farther...

halogens

Halogens: Trends and Reactions

Halogens are Group 17 nonmetals that show clear trends in structure and reactivity. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Astatine is highly unstable and radioactive, so most of its properties are still unknown because it has a very short half-life. Tennessine is a synthetic element that is also predicted to belong to this group. These elements do not usually exist as single atoms. Instead, they form diatomic molecules, which means...

noble gases

Noble Gases: Sources, Uses, and Reactions

Noble gases are the group 18 elements helium, neon, argon, krypton, xenon, and radon. They were called “noble” because they were once thought to be nonreactive. That idea changed in 1962, when Dr. Neil Bartlett at the University of British Columbia showed that this assumption was not fully correct. These gases occur in very small amounts in the atmosphere. Some natural gas contains 1–2% helium by mass. Helium is separated from natural gas by removing the condensable components, which leaves...

key terms and concepts

Learn how valence electrons explain periodic table groups, blocks, and element behavior, including main group, transition, lanthanide, and actinide elements.

How Valence Electrons Shape the Periodic Table | JoVE K12

chemistry

JoVE Core Química da vida a los conceptos de química general mediante lecciones de vídeo basadas en animaciones, concisas y fáciles de entender. Además, en los vídeos de científicos en acción, se muestran experimentos de investigación clásicos y originales realizados en laboratorios de todo el mundo.

Physical Science

PS.PSc.1.6

Pennsylvania State Academic Standards

Chemical Reactions

3.2.9-12.C

Structure and Properties of Matter

3.2.9-12.A

Louisiana Student Standards for Science

High School

Matter And Its Interactions

HS-PS1-1

HS-PS1-2

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Study Of Matter

Periodic trends of the elements

Structure And Properties Of Matter

Periodic Table

Tennessee Academic Standards

Matter and Its Interactions

CHEM1.PS1.12

Virginia  Standards of Learning

HIgh School

CH.2

CH.2.b

CH.2.c

PS.2

PS.2.b

PS.4

PS.4.a

PS.4.b

Minnesota Academic Standards in Science

3.1.1 9C.2.1.1.1

9C.3.1.1.1

Arizona Science Standards

HS.P1

HS.P1U1.1

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

Texas Essential Knowledge and Skills

CHEM.5

CHEM.5.A

Alabama Course of Study Science

9-12.C.1.1

9-12.C.1.1.e

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

9-12.C.2.2.f

9-12.PS.3.4.b

Next Generation Science Standards

Florida Department of Education

SC.912.P.8

SC.912.P.8.5

Chemistry and Physics

IPC.7

IPC.7.A

IPC.7.B

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

South Carolina College and Career Ready Science Standards

C-PS1-2

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Structure and Properties of Matter

HS-PS1-1.

Georgia Standards of Excellence

SPS1.

Periodic Table Trends

SC1.

periodic-table-trends-atomic-radii-ionization-and-electronegativity

Periodic Table Trends: Atomic Radii, Ionization, and Electronegativity

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

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.

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 ...

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

Analyze the structure of atoms and isotopes.

How Valence Electrons Shape the Periodic Table

Description

Transcript

Tags

More videos by Standards