Name: electronegativity and polar bonds
Uploaded: 2020-09-03T13:38:28.000Z
Duration: 2 min 54 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

Electronegativity

Ametaller elektronları paylaşarak kovalent bağlar oluştururlar. Fakat bu elektronlar her iki atom arasında eşit olarak mı paylaşılır, yoksa bir atom elektronları diğerinden daha fazla mı çeker? Lewis modeli, tüm kovalent bağları eşit olarak paylaşılan elektronlar olarak gösterir;ancak bu her zaman böyle değildir.Örneğin, gaz halindeki nitrojen bir elektrik alanına yerleştirilirse, kutuplar arasında eşit olarak yönlendirilecektir. Ancak nötr bir molekül olan gaz halindeki hidrojen klorür bir elektrik alanına yerleştirildiğinde, hidrojen katoda ve kloru anoda doğru yönlendirerek hidrojenin kısmi pozitif yüke ve klorun kısmi negatif yüke sahip olduğunu gösterir. Bir atomun elektronları kendine çekme kabiliyetine elektronegatiflik denir.Böylece klorun hidrojenden daha elektronegatif olduğu, paylaşılan elektronları kendine çekerken kendi elektronlarının çıkarılmasına direndiği söylenir. Ancak bu durum bağı iyonik yapmaz. İyonik bir bağda elektronlar metallerden ametallere aktarılırken, HCl'de elektronlar eşit olmayan şekilde paylaşılır.Elektron yoğunluğu, klorda polar kovalent bir bağ oluşturan hidrojen atomundan daha yüksektir. İki atom arasındaki elektronegatiflik farkı ne kadar büyükse, bağ o kadar polar olacaktır. Bu nedenle, polar olmayan kovalent veya iyonik bağlara ek olarak, çok çeşitli bileşiklerde polar kovalent bağlar bulunur.Amerikalı Kimyager Linus Pauling, diatomik klor veya hidrojen gibi moleküllerdeki bağları kırmak için gereken enerjileri incelemiştir. Bağ türlerini tahmin etmeye yardımcı olan termokimyasal verilere dayalı bir elektronegatiflik ölçeği oluşturmuştur. Elektronegativite, atomların iyonlaşma enerjisi ve elektron afinitesi ile ilişkilidir.Periyodik tabloda, elektronegatiflik değerleri soldan sağa doğru artmaktadır metaller, geçiş metalleri hariç, ametallere göre daha az elektronegatiftir. Ek olarak, elektronegatiflik değerleri sütunda ve atom boyutunun artmasıyla azalır, çünkü atomlar elektronları kendilerine daha az çekebilirler. En elektronegatif element olan florine, rasgele olarak 3, 98'lik bir elektronegatiflik değeri atanmıştır.Fransiyum ise 0, 7'lik bir elektronegatiflik değeri ile en az elektronegatif elementtir. Elektronegativitenin birimi yoktur;deneysel olarak belirlenemez.

elektronegatiflik

Bir bağın apolar veya polar kovalent olup olmadığı, elektronegatiflik adı verilen bağ atomlarının bir özelliği ile belirlenir. 
 
 Elementlerin elektronegatiflik değerleri, yirminci yüzyılın en ünlü kimyagerlerinden biri olan Linus Pauling tarafından önerilmiştir. Pauling, hidrojen ve florür gibi heteronükleer moleküllerdeki bağları kırmak için gereken enerjileri araştırdı. Değerlere dayanarak, bir bağı kırmak için gereken enerjinin, H2'nin (436 kJ/mol) ve F2'nin (155 kJ/mol) bağ enerjilerinin ortalaması, yani 296 kJ/mol mol olacağını öne sürdü. Bununla birlikte, HF'nin deneysel olarak elde edilen bağ enerjisi, tahmin edilen değerden çok daha yüksek olan 565 kJ/mol'dür. Bu farkı hesaba katmak için Pauling, bağın elektronegatiflik kavramıyla belirlenen iyonik bir karaktere sahip olması gerektiğini öne sürdü. 
 
 Elektronegatiflik, bir atomun elektronları (veya elektron yoğunluğunu) kendine çekme eğiliminin bir ölçüsüdür. 
 
 Elektronegatiflik, paylaşılan elektronların bir bağdaki iki atom arasında nasıl dağıldığını belirler. Bir atom, bağlarındaki elektronları ne kadar güçlü çekerse, elektronegatifliği o kadar büyük olur. Polar kovalent bağdaki elektronlar daha elektronegatif atoma doğru kaydırılır; bu nedenle, daha fazla elektronegatif atom, kısmi negatif yüklü olandır. Elektronegatiflikteki fark ne kadar büyük olursa, elektron dağılımı o kadar polarize olur ve atomların kısmi yükleri o kadar büyük olur.
 
 <h4>Elektronegatiflik ve Periyodik Tablo Table</h4>
 
 <ul>
 <li>Elektronegatiflik, periyodik tablodaki bir periyot boyunca soldan sağa doğru artar ve bir grupta aşağı gidildikçe azalır. </li>
 <li>Pauling tarafından türetilen elektronegatiflik değerleri, periyodik tablonun sağ üst köşesine doğru daha yüksek elektronegatifliklerle öngörülebilir periyodik eğilimleri takip eder.</li>
 <li>Bu nedenle, sağ üstte yer alan ametaller en yüksek elektronegatifliğe sahip olma eğilimindedir, flor hepsinin en elektronegatif elementtir (EN = 4.0). </li>
 <li>Metaller daha az elektronegatif elementler olma eğilimindedir ve grup 1 metaller en düşük elektronegatifliğe sahiptir. </li>
 <li>Soy gazlar, elektronegatiflik listesinin dışında tutulur çünkü bu atomlar, tam bir değerlik kabuğuna sahip oldukları için genellikle elektronları diğer atomlarla paylaşmazlar. (XeO2 gibi asal gaz bileşikleri mevcut olmakla birlikte, yalnızca aşırı koşullar altında oluşturulabilirler ve bu nedenle genel elektronegatiflik modeline tam olarak uymazlar.)</li>
 </ul>
 
 <h4>Elektronegatiflik ve Elektron Afinitesi</h4>
 
 Elektronegatiflik ve elektron afinitesini karıştırmamaya dikkat edin. Bir elementin elektron ilgisi ölçülebilir bir fiziksel niceliktir, yani izole edilmiş bir gaz fazı atomu bir elektron aldığında açığa çıkan veya absorblanan enerjidir ve kJ/mol cinsinden ölçülür. Öte yandan, elektronegatiflik, bir atomun bir bağdaki elektronları ne kadar sıkı çektiğini açıklar. Ölçülmeyen, hesaplanan boyutsuz bir miktardır. Pauling, ilk elektronegatiflik değerlerini, farklı bağ türlerini kırmak için gereken enerji miktarlarını karşılaştırarak elde etti. 0 ile 4 arasında keyfi bir göreceli ölçek seçti.
 
 Bu metin bu kaynaktan uyarlanmıştır: <a href="https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding">Openstax, Chemistry 2e, Section: 7.2 Covalent Bonding.</a>

Elektronegatiflik

Bir bağın polar olmayan veya polar kovalent olup olmadığı, bağ atomlarının elektronegatiflik adı verilen bir özelliği ile belirlenir. 

Elektronegatiflik değerleri ...

Education

JoVE Core

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Chemical Bonding: Basic Concepts

Kimyasal Bağlanma: Temel Kavramlar

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

electronegativity and polar bonds

Electronegativity helps explain why some covalent bonds are nonpolar and others are polar covalent. It is a measure of how strongly an atom attracts shared electrons toward itself. That pull controls how electron density is distributed in a bond.

Linus Pauling proposed the first electronegativity values by studying bond energies in heteronuclear molecules such as hydrogen fluoride. He expected the bond energy of HF to be about the average of the bond energies of H2 and F2, or 296 kJ/mol. The experimental bond energy of HF was much higher, at 565 kJ/mol, which suggested the bond had some ionic character.

In a polar covalent bond, the shared electrons shift toward the more electronegative atom. That atom carries the partial negative charge. The larger the electronegativity difference between two atoms, the more the electrons are pulled to one side, and the larger the partial charges become.

Electronegativity follows clear periodic trends. It increases from left to right across a period and decreases down a group. As a result, the highest values are found toward the upper right of the periodic table, especially among nonmetals. Fluorine is the most electronegative element, with a value of 4.0, while group 1 metals have the lowest values. Noble gases are usually left off electronegativity lists because they already have full valence shells and usually do not share electrons. Some noble gas compounds, such as XeO2, can form only under extreme conditions.

Do not confuse electronegativity with electron affinity. Electron affinity is the measurable energy released or absorbed when an isolated gas-phase atom gains an electron. Electronegativity is different. It describes how strongly an atom attracts electrons in a bond, so it is calculated rather than measured. Pauling placed these values on an arbitrary relative scale from 0 to 4.

Electronegativity and Polar Bonds

types of chemical bonds

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electronegativity

Electronegativity helps explain why some covalent bonds are nonpolar and others are polar covalent. It is a measure of how strongly an atom attracts shared electrons toward itself. That pull controls how electron density is distributed in a bond. Linus Pauling proposed the first electronegativity values by studying bond energies in heteronuclear molecules such as hydrogen fluoride. He expected the bond energy of HF to be about the average of the bond energies of H2 and F2, or 296 kJ/mol. The...

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lewis structures of molecular compounds and polyatomic ions

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Learn how electronegativity explains polar covalent bonds, Pauling’s bond-energy idea, periodic trends, and the difference from electron affinity.

Electronegativity and Polar Bonds | JoVE K12

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Electronegativity and Polar Bonds

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