Name: atomic orbitals and quantum numbers
Uploaded: 2023-04-30T18:28:31.000Z
Duration: 2 min 28 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Matter And Its Interactions

HS-PS1-1

Electronic Structure of Atoms

Un atomo è composto da tre particelle subatomiche: elettroni, protoni e neutroni. I protoni caricati positivamente e i neutroni elettricamente neutri costituiscono il nucleo atomico, dove risiedono tutta la carica positiva e la maggior parte della massa di un atomo.
Gli elettroni sono i costituenti caricati negativamente e di piccola massa situati nello spazio vuoto attorno al nucleo. Un atomo è elettricamente neutro quando ha tanti elettroni quanti protoni.
Gli elettroni presentano una duplice natura: particella e onda. La loro posizione nello spazio e la loro energia sono proprietà complementari. Pertanto, per un elettrone con un'energia ben definita, la sua posizione è incerta.
Il modello meccanico quantistico di un atomo prevede che la probabilità di trovare un elettrone di una data energia in una regione tridimensionale nello spazio può essere determinata dal quadrato della funzione d'onda che esprime la natura ondulatoria dell'elettrone, chiamata anche densità di probabilità elettronica.
Una funzione che descrive la probabile posizione spaziale di un elettrone di energia specifica in un atomo è chiamata orbitale atomico.
Ogni orbitale corrisponde a una combinazione unica di tre numeri quantici. Il numero quantico principale, n, raggruppa gli orbitali in livelli di energia o gusci.
Il momento angolare, o azimutale, numero quantico, l, raggruppa gli orbitali all'interno delle conchiglie in sottogusci. Ogni valore di l corrisponde a un orbitale s, p, d o f di forma variabile.
Alcune forme orbitali possono avere più orientamenti possibili, ciascuno associato a un numero quantico magnetico, ml. Il numero di orientamenti per una data sottoshell è uguale a due-l più uno.
Il quarto numero quantico - il numero quantico di spin, ms - è associato agli elettroni che occupano un orbitale e ha solo due valori possibili: 'più la metà' e 'meno la metà'. Ciò garantisce che due elettroni in un atomo non abbiano gli stessi valori per tutti e quattro i numeri quantici.
La sovrapposizione degli orbitali l'uno sull'altro produce una forma approssimativamente sferica, come una "nuvola" di elettroni che circonda il nucleo. Questo è il motivo per cui gli atomi sono generalmente rappresentati come sfere.

struttura elettronica degli atomi

Un atomo è composto da protoni e neutroni, che sono contenuti all'interno della parte centrale densa chiamata nucleo, e da elettroni presenti attorno ad esso. Tenendo conto della dualità onda-particella degli elettroni e dell’incertezza della posizione attorno al nucleo, la meccanica quantistica fornisce un modello più accurato della struttura atomica. Descrive gli orbitali atomici come le regioni attorno al nucleo in cui esistono elettroni con discreta energia, caratterizzate da quattro numeri quantici: n, l, ml e ms.

Modello Quanto-meccanico

Un atomo è costituito da un piccolo nucleo carico positivamente circondato da elettroni. Il nucleo contiene protoni e neutroni. I protoni hanno carica +1 e massa 1.0073 amu. I neutroni hanno carica nulla e una massa di 1,0087 amu. Gli elettroni hanno una carica pari a −1 e una massa pari a 0,00055 amu. Il numero di protoni nel nucleo è chiamato numero atomico (Z) e definisce l’identità elementare di un atomo. La somma del numero di protoni e neutroni nel nucleo è chiamata numero di massa e, espressa in amu, è approssimativamente uguale alla massa dell'atomo. Un atomo è neutro quando contiene un numero uguale di elettroni e protoni.

Sono stati proposti vari modelli per descrivere la struttura atomica e spiegare la distribuzione degli elettroni attorno al nucleo. La relazione di de Broglie quantifica che gli elettroni hanno sia le proprietà di una particella che di un'onda. Quantificando ulteriormente questo dualismo onda-particella, Heisenberg fornì il principio di indeterminazione: la posizione (associata alla natura particellare) e la velocità o l'energia (associata alla natura ondulatoria) dell'elettrone non possono essere determinate simultaneamente con piena precisione. Il modello quanto-meccanico fornisce un quadro più accurato della struttura atomica. Descrive la posizione tridimensionale di un elettrone con energia specifica, contenuto in un atomo, in modo probabilistico in termini del quadrato della funzione d'onda, ψ^2. Le funzioni d'onda atomiche, o orbitali atomici, descrivono le regioni di un atomo in cui è più probabile che si trovino gli elettroni.

Un orbitale atomico è caratterizzato da tre numeri quantici. Il numero quantico principale, n, raggruppa gli orbitali in termini di posizione del livello energetico, o “guscio”. Il momento angolare o numero quantico azimutale, l, raggruppa gli orbitali in “sottolivelli” in base alla loro forma. Ha valori interi da 0 a n – 1 ed è rappresentato dalle lettere: s (l = 0), p (l = 1), d (l = 2), f (l = 3), g (l = 4) e h (l = 5). Il numero quantico magnetico, ml, con valori 2l + 1 compresi tra –l e +l, descrive l'orientamento dell'orbitale nello spazio. Inoltre, ogni elettrone ha un numero quantico di spin, ms, che può essere uguale a ±1/2. Non esistono due elettroni nello stesso atomo che possano avere lo stesso insieme di valori per tutti e quattro i numeri quantici.

Questo testo è adattato da <a href="https://openstax.org/books/chemistry-2e/pages/6-3-development-of-quantum-theory#0"> Openstax, Chemistry 2e, Section 6</a>

Struttura elettronica degli atomi


Un atomo comprende protoni e neutroni, che sono contenuti all'interno del nucleo centrale denso chiamato nucleo, con elettroni presenti intorno al ...

Education

Didattica

JoVE Core

Organic Chemistry

Chimica Organica

Unit 1

Unità 1

Covalent Bonding and Structure

Legame covalente e struttura

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

atomic orbitals and quantum numbers

Atomic orbitals and quantum numbers describe how electrons are arranged around the nucleus. An atom has a small, positively charged nucleus with electrons surrounding it. The nucleus contains protons and neutrons, and the quantum mechanical model gives a better picture of this structure than older models.

Protons carry a +1 charge and have a mass of 1.0073 amu. Neutrons have no charge and have a mass of 1.0087 amu. Electrons carry a −1 charge and have a mass of 0.00055 amu. The number of protons is the atomic number, Z, and it defines the element. The total number of protons and neutrons is the mass number, and it is approximately equal to the atom’s mass in amu. An atom is neutral when it has equal numbers of protons and electrons.

The quantum model grew from ideas about electron behavior. The de Broglie relation showed that electrons act like both particles and waves. Heisenberg’s uncertainty principle added that an electron’s position and its velocity or energy cannot both be known with full precision at the same time. Because of this, electron location is described in a probabilistic way using the square of the wavefunction, ψ².

Atomic wavefunctions, or atomic orbitals, show the regions where electrons are most likely to be found. Orbitals are described by four quantum numbers. The principal quantum number, n, gives the energy level or shell. The angular momentum, or azimuthal, quantum number, l, describes orbital shape and forms subshells. Its values run from 0 to n − 1, and the labels are s, p, d, f, g, and h for l = 0 through 5.

The magnetic quantum number, ml, describes how an orbital is oriented in space. It has 2l + 1 possible values, ranging from −l to +l. The spin quantum number, ms, can be +1/2 or −1/2. No two electrons in the same atom can have the same set of values for all four quantum numbers.

Atomic Orbitals and Quantum Numbers

what is organic chemistry?

Carbon Compounds in Everyday Life

Organic chemistry focuses on carbon compounds called organic compounds. These compounds may come from living things or be made by chemists. Carbon is the main element in them, and it bonds with other carbon atoms as well as hydrogen, oxygen, nitrogen, and sulfur. Carbon can form up to four strong bonds. That ability lets carbon atoms build chains and rings of many sizes, shapes, and levels of complexity. Not every carbon-containing substance is classified as organic. Carbonates, cyanides, and...

electronic structure of atoms

Atomic orbitals and quantum numbers describe how electrons are arranged around the nucleus. An atom has a small, positively charged nucleus with electrons surrounding it. The nucleus contains protons and neutrons, and the quantum mechanical model gives a better picture of this structure than older models. Protons carry a +1 charge and have a mass of 1.0073 amu. Neutrons have no charge and have a mass of 1.0087 amu. Electrons carry a −1 charge and have a mass of 0.00055 amu. The number of...

electron configurations

How Electrons Fill Atomic Orbitals

Electron filling in atoms follows a set order based on orbital energy. The Aufbau principle says each new electron enters the lowest-energy subshell available. The Pauli exclusion principle says no two electrons can share the same set of four quantum numbers. Hund’s rule of maximum multiplicity says electrons stay unpaired in equal-energy orbitals when possible. The order of filling follows the relative energies of the subshells. A common sequence is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on.

chemical bonds

Chemical Bonds: Types and Strength

Chemical bonds help atoms reach a full valence shell like the nearest noble gas. The main bond types are ionic, covalent, and metallic. Bond energy and bond length also help explain how strong a bond is. An ionic bond forms from electrostatic attraction between cations and anions. In many cases, one atom transfers electrons to another atom, and the ions form from that transfer. Ionic bonds have no defined direction because the attraction spreads evenly through three-dimensional space. A...

polar covalent bonds

Electronegativity in Polar Covalent Bonds

Polar covalent bonds form when atoms share electrons unevenly. This happens in covalent bonds between atoms that have similar, but not identical, tendencies to attract electrons. Nonmetal atoms often make these bonds with other nonmetals. Hydrogen gas, H2, is a simple example of a covalent bond between two hydrogen atoms. A covalent bond begins when two atoms move close enough for their valence orbitals to overlap. In hydrogen, the 1s orbitals overlap and the single electrons on each atom...

lewis structures and formal charges

Lewis Structures, Bonds, and Formal Charge

Lewis structures show how atoms share electrons in covalent bonds and in polyatomic ions. Lewis symbols help draw these structures, and the periodic table helps predict how many valence electrons an atom has and how many bonds it can form to reach an octet. Group 18 elements, such as argon and helium, already have filled electron configurations. They rarely take part in chemical bonding. Atoms in group 17, such as bromine and iodine, need one more electron to reach an octet, so they can form...

vsepr theory

Molecular Shapes from Electron Pairs

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molecular geometry and dipole moments

Predicting Shape and Molecular Polarity

Molecular shape and molecular polarity can be predicted with VSEPR theory and dipole moments. Start by writing the Lewis structure of the molecule or polyatomic ion. Then count the electron groups around the central atom. Lone pairs and bonds both count as electron groups, and a single, double, or triple bond each counts as one region of electron density. Use that count to identify the electron-pair geometry. Next, use the number of lone pairs to determine the molecular structure. If more than...

resonance and hybrid structures

Resonance in Nitrite and Carbonate Ions

Resonance explains why some Lewis structures do not match the measured properties of a molecule or ion. When two or more Lewis structures have the same atom arrangement, the real electron distribution is an average of the structures shown. The nitrite anion, NO2−, is one example. It can be drawn in two ways, with the N–O and N=O bonds in different places. If nitrite had one single bond and one double bond, the two bond lengths should be different, because a double bond is shorter and stronger...

valence bond theory and hybridized orbitals

valence-bond-theory-and-hybridized-orbitals

Covalent Bond Overlap and Orbital Hybridization

Covalent bonds form when orbitals on two atoms overlap and their single electrons pair up. The bond is stronger when the overlap is greater. Maximum overlap happens when the orbitals meet along a direct line between the two nuclei. A sigma bond, or σ bond, is the kind of covalent bond found in a single bond in a Lewis structure. In a σ bond, electron density is concentrated along the internuclear axis. A pi bond, or π bond, forms when two p orbitals overlap side by side. In a π bond, the...

mo theory and covalent bonding

Bond Order and Molecular Orbitals

Molecular orbital theory explains how electrons are arranged in molecules. It treats electron regions in a molecule much like atomic orbitals in an atom. A molecular orbital is the region of space where a valence electron is most likely to be found. Molecular orbitals form through the linear combination of atomic orbitals, or LCAO. When atomic wave functions combine in phase, they create regions with high electron density. When they combine out of phase, they create nodes, or regions with no...

intermolecular forces and physical properties

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How Intermolecular Forces Affect Matter

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solubility

Why Some Substances Dissolve in Water

Solution formation depends on how solutes and solvents interact. A solution is a homogeneous mixture made of a solvent, which is the larger part, and a solute, which is the smaller part. The physical state of a solution is usually the same as the solvent. Concentration is often described as dilute for a low amount of solute or concentrated for a high amount of solute. When a solute dissolves, its particles are surrounded by solvent species. This process is called solvation. If water is the...

introduction to functional groups

Functional Groups and Organic Molecules

Functional groups are groups of atoms with specific chemical properties that appear within organic molecules. They are sometimes shown as "R." These groups sit along the carbon backbone of macromolecules, which can form chains or rings of carbon atoms. Functional groups help functionalize a compound. That means they can give the molecule different physical and chemical properties. In organic chemistry, this change in group structure can strongly affect how a compound behaves. Common...

overview of advanced functional groups

Advanced Functional Groups in Organic Chemistry

Advanced functional groups are atom clusters in organic molecules that give those molecules specific chemical properties. They are sometimes shown as "R" in formulas. By changing the atoms attached to a carbon skeleton, a functional group can make a compound behave differently in physical and chemical reactions. This topic covers several major classes of organic compounds with advanced functional groups. Aromatic hydrocarbons include benzene. Phenol is another example and is also called...

key terms and concepts

Learn how atomic orbitals, shells, subshells, and the four quantum numbers describe electron arrangement in atoms through the quantum mechanical model.

Atomic Orbitals and Quantum Numbers | JoVE K12

organic chemistry

JoVE Core Organic Chemistry spiega i concetti di base della stereochimica, delle reazioni e dei meccanismi usando video-lezioni concise e facili da capire. Inoltre, i video scientist-in-action dimostrano l'applicazione di tali concetti in esperimenti di ricerca classici e originali eseguiti al giorno d'oggi nei laboratori in tutto il mondo.

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Motion And Stability: Forces And Interactions

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Physical Science

Matter and Its Interactions

Florida Department of Education

SC.912.P.8

SC.912.P.8.5

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South Carolina College and Career Ready Science Standards

C-PS1-1

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Motion and Stability: Forces and Interactions

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Physics

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Ions and Ionic Charges

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HS-PS1-4

Atomic Orbitals and Quantum Numbers

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