Name: how ionic charge changes ion size
Uploaded: 2020-09-03T13:38:28.000Z
Duration: 3 min 10 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.2.2

Ionic Radii

Un raggio ionico è il raggio di un catione o di un anione, definito dalla distanza tra gli ioni in un composto ionico. I cationi sono più piccoli dell'atomo originario, mentre gli anioni sono più grandi. Simile ai raggi atomici, i raggi ionici sono determinati dal numero di elettroni, dagli orbitali che ne contengono gli elettroni di valenza e dalla carica nucleare.

Considerate il litio, che ha una configurazione degli elettroni di un core di elio con un elettrone 2s più esterno. L'elettrone 2s è schermato dalla carica nucleare da due elettroni 1s e corrisponde ad un raggio atomico di 152 picometri. La perdita dell'elettrone 2s più esterno genera un catione di litio, che ha meno elettroni, ma lo stesso numero di protoni dell'atomo iniziale.

I due elettroni 1s sono tenuti più vicini al nucleo perché sperimentano una carica nucleare efficace maggiore rispetto all'elettrone 2s. Pertanto, il raggio ionico del catione di litio è di 60 picometri, che è molto più piccolo dell'atomo di origine. Questa tendenza è generalmente osservata con tutti i cationi metallici e i loro atomi derivati.

Al contrario, gli anioni sono più grandi dei loro atomi di origine. Quando un atomo di fluoro accetta un elettrone, ottiene un ulteriore elettrone più esterno, ma il numero di protoni, e quindi la carica nucleare, rimane la stessa. L'aumento della repulsione elettrone-elettrone fa sì che gli elettroni si diffondano maggiormente nello spazio.

Pertanto, l'anione fluoruro ha un raggio di 136 picometri, che è molto più grande dell'atomo originario. In generale, il raggio ionico per gli elementi del blocco s e p aumenta lungo la colonna, all'aumentare del numero dei principali livelli di energia, e quindi del numero di orbitali. Che dire di un gruppo di atomi e ioni che possiedono lo stesso numero di elettroni?

Questi sono indicati come una serie isoelettronica e possono essere disposti in base al numero atomico crescente. Ogni membro della serie isoelettronica raffigurata ha 18 elettroni. Tuttavia, differiscono nel numero di protoni.

Lo ione solfuro ha 16 protoni che attraggono 18 elettroni, mentre lo ione calcio ha 20 protoni che attraggono lo stesso numero di elettroni. Pertanto, con più protoni, il calcio può attirare gli elettroni molto più vicini al nucleo rispetto al solfuro, con il risultato che lo ione calcio è più piccolo dello ione solfuro. Maggiore è la carica nucleare, minore è il raggio, anche se l'aggiunta di un guscio di elettroni interrompe questa tendenza.

In conclusione, il solfuro è il più grande e il calcio è lo ione più piccolo di questa serie.

raggi ionici

Il raggio ionico è la misurazione utilizzata per descrivere la dimensione di uno ione. Un catione ha sempre meno elettroni e lo stesso numero di protoni dell'atomo genitore; è più piccolo dell'atomo da cui deriva. Ad esempio, il raggio covalente di un atomo di alluminio (1s22s22p63s23p1) è 118 pm, mentre il raggio ionico di un Al3+ (1s22s22p6) è 68 pm. Quando gli elettroni vengono rimossi dal guscio di valenza esterno, gli elettroni rimanenti del nucleo che occupano gusci più piccoli sperimentano una carica nucleare Zef più effettiva e vengono attratti ancora più vicini al nucleo.

I cationi con cariche maggiori sono più piccoli dei cationi con cariche minori (ad esempio, V2+ ha un raggio ionico di 79 pm, mentre quello di V3+ è 64 pm). Procedendo verso il basso lungo i gruppi della tavola periodica, i cationi di elementi successivi con la stessa carica hanno generalmente raggi maggiori, corrispondenti ad un aumento del numero quantico principale, n.

Un anione (ione negativo) si forma mediante l'aggiunta di uno o più elettroni al guscio di valenza di un atomo. Ciò si traduce in una maggiore repulsione tra gli elettroni e una diminuzione di Zeff per elettrone. Entrambi gli effetti (l'aumento del numero di elettroni e la diminuzione dello Zeff) fanno sì che il raggio di un anione sia maggiore di quello dell'atomo genitore. Ad esempio, un atomo di zolfo ([Ne]3s23p4) ha un raggio covalente di 104 pm, mentre il raggio ionico dell'anione solfuro ([Ne]3s23p6) è di 170 pm. Per gli elementi consecutivi che procedono verso il basso in qualsiasi gruppo, gli anioni hanno numeri quantici principali maggiori e, quindi, raggi maggiori.

Gli atomi e gli ioni che hanno la stessa configurazione elettronica si dicono isoelettronici. Esempi di specie isoelettroniche sono N3–, O2–, F–, Ne, Na+, Mg2+, and Al3+ (1s22s22p6). Un'altra serie isoelettronica è P3–, S2–, Cl–, Ar, K+, Ca2+, e Sc3+ ([Ne]3s23p6). Per gli atomi o gli ioni isoelettronici, il numero di protoni determina la dimensione. Maggiore è la carica nucleare, minore è il raggio in una serie di ioni e atomi isoelettronici.

Questo testo è adattato da <a href="https://openstax.org/books/chemistry-2e/pages/6-5-periodic-variations-in-element-properties">OpenStax Chemistry 2e, Section 6.5: Periodic Variations in Element Properties.</a>

Raggi ionici

Il raggio ionico è la misura utilizzata per descrivere la dimensione di uno ione. Un catione ha sempre meno elettroni e lo stesso numero di protoni dell'atomo genitore; esso...

Education

Didattica

JoVE Core

Chimica

Periodic Properties of the Elements

Proprietà periodiche degli elementi

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 draws them closer to the nucleus.

Cations with larger charges are usually smaller than cations with smaller charges. For example, V2+ has an ionic radius of 79 pm, while V3+ is smaller at 64 pm. Moving down a group in the periodic table, cations with the same charge generally get larger. This happens because the principal quantum number, n, increases.

Anions are negative ions formed when one or more electrons are added to the valence shell. Extra electrons increase electron repulsion and reduce Zeff per electron. Both effects make an anion larger than its parent atom. Sulfur is an example: a sulfur atom has a covalent radius of 104 pm, while the sulfide anion has an ionic radius of 170 pm. Anions also tend to have larger radii down a group because n increases.

Atoms and ions with the same electron configuration are called isoelectronic. One example set is N3−, O2−, F−, Ne, Na+, Mg2+, and Al3+, which all have the same electron arrangement. Another is P3−, S2−, Cl−, Ar, K+, Ca2+, and Sc3+. In an isoelectronic series, the number of protons controls size. The greater the nuclear charge, the smaller the radius.

How Ionic Charge Changes Ion Size

periodic classification of the elements

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...

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

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 cations and anions change size, why ionic radius varies with charge, and how isoelectronic species compare across the periodic table.

How Ionic Charge Changes Ion Size | 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.

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.c

PS.2

PS.2.b

PS.4

PS.4.a

PS.4.b

Arizona Science Standards

HS+C.P1

HS+C.P1U1.1

Texas Essential Knowledge and Skills

CHEM.5

CHEM.5.A

CHEM.5.C

CHEM.7

CHEM.7.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

Chemistry and Physics

IPC.7

IPC.7.B

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Structure and Properties of Matter

HS-PS1-1.

HS. Chemical Reactions

HS-PS1-2.

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

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

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 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.

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 ...

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 Ionic Charge Changes Ion Size

Description

Transcript

Tags

More videos by Standards