Name: predicting ionic stability with lattice energy
Uploaded: 2020-09-03T13:38:28.000Z
Duration: 2 min 44 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.3.1

The Born-Haber Cycle

İyonik bağların oluşumu, bir metalden ametal atoma elektron aktarımı ile gerçekleşir bu genellikle endotermik bir süreçtir. Bununla birlikte, sodyum ve klor elementleri, katı bir sodyum 5 00:00:13, 170 000:16, 447 klorür kristali oluşturmak için reaksiyona girdiğinde, bu oldukça ekzotermik bir süreçtir. Peki bu enerji nereden geliyr?Coulomb yasasına göre, katyonlar ve anyonlar güçlü elektrostatik kuvvetler tarafından katı bir diziye veya kafese çekilir. Ortaya çıkan kafes yapısı, ısı olarak salınan potansiyel enerjinin ekzotermik bir reaksiyonla azaltılmasıyla stabilize edilir. Bir kristal kafesin gaz bileşenlerine dönüşmesi veya bozulmasıyla ilişkili toplam enerjiye kafes enerjisi denir.Katı iyonik bir bileşikte, çok sayıda yüklü parçacık birbirleriyle etkileşime girerek kafes enerjisinin tam değerini deneysel olarak belirlemeyi zorlaştırır. Bununla birlikte, Hess yasası kullanılarak, kurucu elementlerinden iyonik bir bileşiğin oluşumunu temsil eden Born Haber döngüsü adı verilen varsayımsal bir dizi adımda hesaplanabilir. Örneğin, sodyum klorür oluşumu için Born-Haber döngüsü, biri doğrudan diğeri dolaylı olmak üzere iki alternatif yolu dikkate alır.Doğrudan yolda, sodyum ve klor elementlerinden NaCl oluşumunun standart entalpisini temsil eder. Dolaylı yolun beş adımı vardır. Birinci aşamada, katı hal sodyum, gaz halindeki şekline dönüştürülür.Daha sonra, iki atomlu klor molekülleri, gaz halindeki klor atomlarına ayrışır. Üçüncü ve dördüncü adımlar iyonları oluşturmak için elektron transferini açıklar. Gaz halindeki sodyumdan bir elektron çıkarılır ve bir sodyum katyonu oluşturulur.Elektron daha sonra bir klorür anyonu oluşturmak üzere gaz halindeki klor tarafından alınır. Son aşamada, gaz halindeki iyonlar arasındaki elektrostatik çekim, kafes yapısının oluşumuna yol açar. Hess yasası, aşamalı bir sürecin toplam entalpisindeki değişimin, her adımdaki entalpi değişikliklerinin toplamı olduğunu belirtir.Direkt yolun entalpi değerinin anlamı, beş adımın entalpilerinin toplamına eşittir. Kafes enerjisi denklemini çözerek, ekzotermik reaksiyonu ifade eden büyük negatif yönlü bir değer belirlenir.

born-haber döngüsü

<h4>Örgü Enerjisi </h4>
 
 İyonik bir bileşik, pozitif ve negatif iyonları arasındaki elektrostatik çekim nedeniyle kararlıdır. Bir bileşiğin örgü enerjisi, bu çekim gücünün bir ölçüsüdür. Bir iyonik bileşiğin örgü enerjisi (ΔHlattice) bir mol katıyı gaz iyonlarına dönüştürmek için gerekli olan enerji olarak tanımlanır. 
 
 Burada, iyonik katının iyonlara ayrıldığı, yani örgü enerjilerinin endotermik olacağı (pozitif değerler) konvansiyon kullanılır. Başka bir yol, eşdeğer, ancak zıt bir kural kullanmaktır, burada örgü enerjisi ekzotermiktir (negatif değerler) ve iyonlar bir örgü oluşturmak için birleştiğinde salınan enerji olarak tanımlanır. Bu nedenle, başka bir referanstaki örgü enerjilerine bakarken hangi tanımın kullanıldığını doğruladığınızdan emin olun. 
 
 Her iki durumda da, büyük bir örgü enerjisi, daha kararlı bir iyonik bileşiği gösterir. Sodyum klorür için ΔHlattice = 769 kJ'dir. Bu nedenle, bir mol katı NaCl'yi gaz halindeki Na+ ve Cl– iyonlarına ayırmak 769 kJ gerektirir. Gaz halindeki Na+ ve Cl– iyonlarının her biri bir mol katı NaCl oluşturduğunda, 769 kJ ısı açığa çıkar.
 
 <h4>İyonik Bir Bileşiğin Örgü Enerjisinin Tayini</h4>
 
 Örgü enerjilerini doğrudan ölçmek mümkün değildir. Bununla birlikte, örgü enerjisi, termokimyasal bir döngü kullanılarak hesaplanabilir. Born-Haber döngüsü, bir iyonik katının oluşumunu bir dizi bireysel adıma ayıran Hess yasasının bir uygulamasıdır:
 
 <table style="margin-left: auto; margin-right: auto;">
 <tbody style="border: 1px solid black;">
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">Cs (k) süblimasyon entalpisi</td>
 <td colspan="2" style="color: black; border: 1px solid black; text-align: center;">Cs (k) → Cs (g)</td>
 <td style="color: black; border: 1px solid black; text-align: center;">ΔH = ΔHk° = 76,5 kJ/mol</td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">F2'nin bağ enerjisinin yarısı</td>
 <td colspan="2" style="color: black; border: 1px solid black; text-align: center;">½ F2 (g) → F (g)</td>
 <td style="color: black; border: 1px solid black; text-align: center;">ΔH = ½ D = 79,4 kJ/mol</td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">Cs (g)'nin iyonlaşma enerjisi</td>
 <td colspan="2" style="color: black; border: 1px solid black; text-align: center;">Cs (g)  → Cs+ (g) + e−</td>
 <td style="color: black; border: 1px solid black; text-align: center;">ΔH = IE = 375,7 kJ/mol</td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">F'nin elektron afinitesi</td>
 <td colspan="2" style="color: black; border: 1px solid black; text-align: center;">F (g) + e− → F− (g)</td>
 <td style="color: black; border: 1px solid black; text-align: center;">ΔH = EA = −328,2 kJ/mol</td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">CsF (s)'nin örgü enerjisinin negatifi</td>
 <td colspan="2" style="color: black; border: 1px solid black; text-align: center;">Cs+ (g) + F− (g) → CsF (k)</td>
 <td style="color: black; border: 1px solid black; text-align: center;">ΔH = −ΔHörgü = ?</td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">CsF (s) oluşum entalpisi, adım 1–5' kadar toplayın</td>
 <td colspan="2" style="color: black; border: 1px solid black; text-align: center;">ΔH = ΔHf° = ΔHs°+ ½ D + IE + (EA) + (−ΔHörgü) 
 Cs (k) + ½ F2 (g) → CsF (k)</td>
 <td style="color: black; border: 1px solid black; text-align: center;">ΔH = −553,5 kJ/mol</td>
 </tr>
 </tbody>
 </table>
 
 <ol>
 <li>Cs (s) ve F2 (g) için en yaygın hallerindeki elementleri düşünün. </li>
 <li>ΔHs°, katı sezyumun gaza dönüşümünü (süblimasyon) temsil eder ve daha sonra iyonizasyon enerjisi, gaz halindeki sezyum atomlarını katyonlara dönüştürür. </li>
 <li>Bir sonraki adımda, flor atomları üretmek için F–F bağını kırmak için gereken enerji hesaba katılmalıdır. </li>
 <li>Bir mol flor atomunu florür iyonlarına dönüştürmek ekzotermik bir süreçtir, bu nedenle bu adım enerji verir (elektron afinitesi). </li>
 <li>Şimdi, bir mol Cs katyonu ve bir mol F anyonu mevcuttur. Bu iyonlar, katı sezyum florür üretmek için birleşir. Bu adımdaki entalpi değişimi, örgü enerjisinin negatifidir, bu nedenle aynı zamanda ekzotermik bir niceliktir. </li>
 <li>Bu dönüşümde yer alan toplam enerji, bileşiğin elementlerinden deneysel olarak belirlenen oluşum entalpisine, ΔHf°'e eşittir. Bu durumda, genel değişim ekzotermiktir.</li>
 </ol>
 
 İyonik bileşikler için hesaplanan örgü enerjileri tipik olarak kovalent bağlar için ölçülen bağ ayrışma enerjilerinden çok daha yüksektir. Örgü enerjileri tipik olarak 600 – 4000 kJ/mol (bazıları daha da yüksek) aralığında değişirken, kovalent bağ ayrışma enerjileri tipik olarak tek bağlar için 150 – 400 kJ/mol arasındadır. Keep in mind, however, that these are not directly comparable values. For ionic compounds, lattice energies are associated with many interactions, as cations and anions pack together in an extended lattice. For covalent bonds, the bond dissociation energy is related to the interaction of just two atoms.
 
 <h4>İyon Yarıçapı ve Yükünün Bir Fonksiyonu Olarak Örgü Enerjisi </h4>
 
 Bir iyonik kristalin örgü enerjisi, iyonların yükleri arttıkça ve iyonların boyutları azaldıkça hızla artar. Diğer tüm parametreler sabit tutulduğunda, hem katyon hem de anyon yükünü iki katına çıkarmak örgü enerjisini dört katına çıkarır. Örneğin, LiF'nin (Z+ and Z– = 1) örgü enerjisi 1023 kJ/mol iken, MgO'nun (Z+ and Z– = 2) 3900 kJ/moldür (Ro = pozitif ve negatif iyonların yarıçaplarının toplamı olarak tanımlanan interiyonik mesafe neredeyse aynıdır - her iki bileşik için yaklaşık 200 pm).
 
 Farklı interatomik mesafeler farklı örgü enerjileri üretmektedir. Örneğin, MgF2'nin örgü enerjisini (2957 kJ / mol) MgI2 (2327 kJ / mol) ile karşılaştırın, bu da I– ile karşılaştırıldığında daha küçük F– iyonik boyutunun kafes enerjisi üzerindeki etkisini gösterir.
 
 <h4>Born-Haber Döngüsünün Diğer Uygulamaları</h4>
 
 Born-Haber döngüsü, geri kalanının bilinmesi koşuluyla, kafes enerjisi için denklemdeki diğer miktarlardan birini hesaplamak için de kullanılabilir. Örneğin, süblimasyon entalpisi  ΔHs°,  iyonizasyon enerjisi (IE), bağ ayrışma entalpisi (D), örgü enerjisi ΔHörgü ve standart oluşum entalpisi  ΔHf°   biliniyorsa, Born-Haber döngüsü bir atomun elektron afinitesini belirlemek için kullanılabilir.
 
 Bu metin bu kaynaktan uyarlanmıştır: <a href="https://openstax.org/books/chemistry-2e/pages/7-5-strengths-of-ionic-and-covalent-bonds">Openstax, Chemistry 2e, Section 7.5: Strengths of Ionic and Covalent Bonds.</a>

Born-Haber Döngüsü

Kafes Enerjisi 

İyonik bir bileşik, pozitif ve negatif iyonları arasındaki elektrostatik çekim nedeniyle kararlıdır. Bir kafes enerjisi ...

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predicting ionic stability with lattice energy

Lattice energy helps explain why ionic compounds are stable. It measures the strength of attraction between positive and negative ions in a crystal. In one common definition, lattice energy is the energy required to separate one mole of an ionic solid into gaseous ions, so it has a positive value. Another definition uses the opposite sign and describes the energy released when gaseous ions form a lattice. When checking data, it is important to confirm which convention is being used. In either case, a larger lattice energy magnitude means a more stable ionic compound.

Sodium chloride gives a simple example. Its lattice energy is 769 kJ/mol, which means 769 kJ is needed to pull one mole of solid NaCl apart into Na+ and Cl- ions in the gas phase. The same amount of heat is released when those ions come together to form solid NaCl. This value shows how strongly the ions attract each other in the crystal.

Lattice energy cannot be measured directly. Instead, it is found with a thermochemical cycle. The Born-Haber cycle uses Hess’s law to break the formation of an ionic solid into separate steps. For cesium fluoride, these steps include sublimation of Cs(s) to Cs(g), half of the F2 bond energy to make F(g), ionization of Cs(g) to Cs+(g) plus an electron, electron affinity of F(g) to make F-(g), and formation of solid CsF from the gaseous ions. The enthalpy change for forming the lattice is the negative of the lattice energy.

For CsF, the overall reaction Cs(s) + 1/2 F2(g) -&gt; CsF(s) has a standard enthalpy of formation of -553.5 kJ/mol. The cycle combines the sublimation enthalpy of cesium, 76.5 kJ/mol, one-half of the F2 bond energy, 79.4 kJ/mol, the ionization energy of cesium, 375.7 kJ/mol, and the electron affinity of fluorine, -328.2 kJ/mol, with the lattice term. Because the total is exothermic, energy is released overall when the solid forms from the elements in their most common states, Cs(s) and F2(g).

Lattice energies for ionic compounds are usually much larger than bond dissociation energies for covalent bonds. Ionic lattice energies often fall between 600 and 4000 kJ/mol, and some are even higher. Single covalent bond dissociation energies are usually about 150 to 400 kJ/mol. These values are not directly comparable because lattice energy reflects many attractions in an extended crystal, while a covalent bond energy describes the interaction of just two atoms.

Ion charge and ion size strongly affect lattice energy. When all other factors stay the same, larger charges give much larger lattice energies, and smaller ions also increase lattice energy. Doubling the charge on both ions can quadruple the lattice energy. For example, LiF has a lattice energy of 1023 kJ/mol, while MgO is 3900 kJ/mol, even though their interionic distances are nearly the same at about 200 pm. Size also matters in compounds such as MgF2 and MgI2, where the smaller F- ion leads to a higher lattice energy than the larger I- ion.

The Born-Haber cycle can also solve for other unknowns in the lattice energy equation. If the other terms are known, the cycle can be used to find a missing quantity such as electron affinity. This makes the method useful for linking measured enthalpy values to the energy changes inside ionic compounds.

Predicting Ionic Stability with Lattice Energy

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types of chemical bonds

Chemical Bonding and Bond Properties

Chemical bonding explains how atoms and ions join to form molecules and compounds. American chemist Gilbert N. Lewis pioneered chemical bonding theory with the Lewis model. This model helps explain why bonds form, why some are stronger than others, and why compounds have fixed formulas like H2O instead of H4O. Ionic bonding involves ions, which are atoms or molecules with an electrical charge. A cation is a positive ion formed when a neutral atom loses one or more electrons from its valence...

the born-haber cycle

Lattice energy helps explain why ionic compounds are stable. It measures the strength of attraction between positive and negative ions in a crystal. In one common definition, lattice energy is the energy required to separate one mole of an ionic solid into gaseous ions, so it has a positive value. Another definition uses the opposite sign and describes the energy released when gaseous ions form a lattice. When checking data, it is important to confirm which convention is being used. In either...

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ionic bonding and electron transfer

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trends in lattice energy: ion size and charge

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Lattice Energy Patterns in Ionic Solids

Lattice energy shows how strongly ions hold an ionic solid together. It is the energy required to separate one mole of a solid into its gaseous ions. For sodium chloride, this process requires 769 kJ per mole. The opposite convention may also be used, where lattice energy is the energy released when gaseous ions form the solid. In either case, a larger magnitude means a more stable ionic compound. For ionic crystals, lattice energy follows a pattern based on charge and ion size. The...

covalent bonding and lewis structures

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lewis structures of molecular compounds and polyatomic ions

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key terms and concepts

Learn how lattice energy, ion charge, ion size, and the Born-Haber cycle help explain ionic stability and calculate values for compounds like CsF.

Predicting Ionic Stability with Lattice Energy | JoVE K12

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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 ...

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

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

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

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.

Analyze the structure of atoms and isotopes.

Predicting Ionic Stability with Lattice Energy

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