Name: electron regions in atomic orbitals
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 44 s
Channel: JoVE

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Atomic Orbitals

Najgęstszy obszar chmury elektronowej – w którym elektron jest najbardziej prawdopodobny – jest opisany w kategoriach orbitali atomowych.  

Kształt orbitala atomowego jest określony przez liczbę kwantową momentu pędu, l. Przypomnijmy, że wartości l są oparte na głównej liczbie kwantowej, n — możliwe wartości l mieszczą się w zakresie od 0 do n − 1. Gdy n jest większe niż jeden, istnieje wiele podpoziomów. Każda wartość l odpowiada orbitalowi s, p, d lub f.

Orbital o najniższej energii to orbital 1s. Jest to sferycznie symetryczny orbital . Gęstość prawdopodobieństwa orbitalu 1s pokazuje, że elektron najprawdopodobniej znajduje się w jądrze. Jednak biorąc pod uwagę siły elektrostatyczne między protonami a elektronami - jest to mało prawdopodobne. 

Pomnożenie gęstości prawdopodobieństwa przez objętość cienkich sferycznych powłok o promieniu r jest bardziej reprezentatywne. Całkowite prawdopodobieństwo znalezienia elektronu w cienkiej powłoce w odległości r od jądra jest funkcją rozkładu radialnego. 

W przypadku wodoru największe prawdopodobieństwo znalezienia elektronu wynosi 52,9 pikometra od jądra. Zatem kształt orbitalu atomowego 1s dla wodoru jest sferyczny o promieniu 52,9 pikometrów.

Orbitale 2s i 3s są również sferyczne. Są większe i mają węzły. W węźle prawdopodobieństwo znalezienia elektronu wynosi zero. 

Główne poziomy z n równym dwóm lub więcej zawierają również trzy orbitale p. Są one w kształcie płata z węzłem w jądrze. Ich orientacja jest opisana przez wartość ml. Trzy orbitale p są do siebie prostopadłe.

Główne poziomy n równe trzem lub więcej mają również pięć orbitali d. Orbitale d o kształcie koniczyny mają cztery płaty o dużej gęstości elektronów i dwie prostopadłe płaszczyzny węzłowe. Jeden z orbitali d jest nieco inny. 

Orbitale f mają więcej płatów i węzłów. Orbitale te istnieją dla głównych poziomów n równych czterem lub więcej. 

Kiedy nałożysz orbitale na siebie, pojawi się mniej więcej kulisty kształt. Dlatego atomy są zwykle przedstawiane jako kule.

orbitale atomowe

Orbital atomowy reprezentuje trójwymiarowe obszary atomu, w których elektron może przebywać z największym prawdopodobieństwem. Funkcja rozkładu radialnego wskazuje całkowite prawdopodobieństwo znalezienia się elektronu w cienkiej powłoce w odległości r od jądra. Orbitale atomowe mają różne kształty, które są określone przez l, liczbę kwantową momentu pędu. Orbitale są często rysowane z powierzchnią graniczną, obejmującą najgęstsze obszary chmury.

Liczba kwantowa momentu pędu jest liczbą całkowitą, która może przyjmować wartości l = 0, 1, 2, …, n – 1. Orbital o głównej liczbie kwantowej 1 (n = 1) może mieć tylko jedną wartość l ( l = 0), podczas gdy główna liczba kwantowa 2 (n = 2) pozwala na l = 0 i l = 1. Orbitale o tej samej wartości l definiują podpowłokę.

Orbitale z l = 0 nazywane są orbitalami s i tworzą podpowłoki s. Wartość l = 1 odpowiada orbitalom p. Dla danego n, orbitale p stanowią podpowłokę p (tj. 3p, jeśli n = 3). Orbitale z l = 2 nazywane są orbitalami d. Orbitale z l = 3, 4 i 5 to orbitale f, g i h.

Orbital o najniższej energii to orbital 1s. Jest to orbital sferycznie symetryczny. Gęstość prawdopodobieństwa (ψ2) orbitalu 1s oznacza, że elektron najprawdopodobniej zostanie znaleziony w jądrze. Na podstawie sił elektrostatycznych pomiędzy protonami i elektronami, nie można dokładnie określić miejsca, w którym elektron będzie się znajdował. Zamiast tego używana jest funkcja rozkładu radialnego, która jest wykresem całkowitego prawdopodobieństwa znalezienia elektronu na orbicie przy danym promieniu r. Funkcję rozkładu radialnego oblicza się, mnożąc gęstość prawdopodobieństwa przez objętość cienkich kulistych powłok o promieniu r. W przypadku orbitalu wodoru 1s funkcja rozkładu radialnego ma w jądrze wartość zero, która wzrasta do maksimum przy 52,9 pikometrów, po czym maleje wraz ze wzrostem r.

Istnieją pewne odległości od jądra, przy których gęstość prawdopodobieństwa znalezienia elektronu znajdującego się na danej orbicie wynosi zero. Innymi słowy, wartość funkcji falowej ψ wynosi zero w tej odległości dla tego orbitalu. Taka wartość r nazywana jest węzłem promieniowym. Liczba węzłów promieniowych na orbicie wynosi n – l – 1. Dla orbitali 2s, gdzie n = 1, istnieje jeden węzeł promieniowy, natomiast orbitale 3s mają dwa węzły promieniowe.

Każdy poziom główny z n = 2 lub więcej zawiera trzy orbitale p. Trzy orbitale p mają dwa płaty z węzłem zlokalizowanym w jądrze. Orientację orbitali p w przestrzeni opisuje wartość ml. Trzy orbitale p są względem siebie prostopadłe (ortogonalne). Wyższe orbitale p (3p, 4p, 5p i więcej) mają podobne kształty, ale są większe i mają dodatkowe węzły promieniowe.

Główne poziomy z n = 3 lub więcej zawierają pięć orbitali d. Cztery z tych orbitali mają kształt czterolistnej koniczyny z czterema listkami o dużej gęstości elektronowej. Istnieją dwie prostopadłe płaszczyzny węzłowe, które przecinają się w jądrze. W tych płaszczyznach węzłowych gęstość elektronów wynosi zero. Jeden z orbitali d ma nieco inny kształt i ma dwa płaty zorientowane w osi z z pierścieniem w kształcie pierścienia w płaszczyźnie xy. Główne poziomy z n = 4 i większymi zawierają siedem orbitali f, które mają złożone kształty. Orbitale te mają więcej węzłów i płatów niż orbitale d.

<img alt="Figure1" src="https://www.jove.com/files/core/CDNSource/lessons/983/983Image 1.png" style="width: 700px;" />

Rysunek 1: Reprezentatywne orbitale s, p, d i f.

Te różne kształty orbitali atomowych reprezentują trójwymiarowe obszary, w których prawdopodobnie znajdzie się elektron. Wszystkie orbitale razem tworzą mniej więcej kulisty kształt, dlatego atomy są zazwyczaj przedstawiane jako kule.

Orbitale atomowe

Orbital atomowy reprezentuje trójwymiarowe obszary w atomie, w których istnieje największe prawdopodobieństwo przebywania elektronu. Rozkład promieniowy ...

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electron regions in atomic orbitals

Electron regions in atomic orbitals show where an electron is most likely to be found in an atom. These three-dimensional regions are often drawn as boundary surfaces around the densest part of the cloud.

The shape of an orbital depends on the angular momentum quantum number, l. This value can range from 0 to n - 1, where n is the principal quantum number. For n = 1, only l = 0 is allowed. For n = 2, both l = 0 and l = 1 are allowed.

Orbitals with the same value of l form a subshell. The l = 0 orbitals are s orbitals, and they make up s subshells. The l = 1 orbitals are p orbitals, which form a p subshell such as 3p when n = 3. The l = 2 orbitals are d orbitals. The l = 3, 4, and 5 orbitals are called f, g, and h orbitals.

The lowest-energy orbital is the 1s orbital. It is spherically symmetric. The probability density, ψ², suggests that an electron is most likely found at the nucleus. But this does not fully match electron behavior. The radial distribution function gives the total probability of finding an electron at a distance r from the nucleus. It is found by multiplying the probability density by the volume of thin spherical shells.

For the 1s orbital of hydrogen, the radial distribution function is zero at the nucleus. It rises to a maximum at 52.9 picometers and then decreases as r increases. Some distances from the nucleus have zero probability density for a given orbital. These points are called radial nodes. The number of radial nodes is n - l - 1. A 2s orbital has one radial node, and a 3s orbital has two.

Each principal level with n = 2 or more contains three p orbitals. Each p orbital has two lobes and a node at the nucleus. Their orientation in space is described by m_l. The three p orbitals are mutually perpendicular. Higher p orbitals, such as 3p, 4p, and 5p, have the same general shape but are larger and contain additional radial nodes.

Principal levels with n = 3 or more contain five d orbitals. Four of them have a cloverleaf shape with four electron-dense lobes. They also have two perpendicular nodal planes that meet at the nucleus. The fifth d orbital has two lobes along the z-axis and a donut-shaped ring in the xy plane.

Principal levels with n = 4 and greater contain seven f orbitals. These orbitals have complex shapes with more nodes and lobes than d orbitals. Together, s, p, d, and f orbitals help explain why atoms are often drawn as spheres, even though the electron regions inside them have distinct shapes.

Electron Regions in Atomic Orbitals

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Electron Regions in Atomic Orbitals

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