Name: lewis structures with formal charge
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Formal Charges

بعض الجزيئات أو الأيونات متعددة الذرات يمكن تمثيلها بواسطة بنيات لويس المتعددة،ولكن كيف تقرر أي واحدة هي البنية المهيمنة؟بحساب الشحنات الرسمية للذرات،بنية لويس الأقرب إلى البنية الفعلية للجزئ،يمكن تحديدها. يتم تعيين شحنة افتراضية لكل ذرة تسمى الشحنة الرسمية،والتي ستكون الشحنة على الذرة إذا كانت جميع الذرات الأخرى في الجزيء لها نفس السالبيةالكهربية. يفترض أن،كل إلكترون رابط،تتقاسمه الذرتان بشكل متساوي.لنضع في اعتبارنا كلوريد الهيدروجين. لتحديد الشحنة الرسمية على كل ذرة،لنقم أولاًبإضافة عدد الإلكترونات غير المترابطة،إلى نصف عدد إلكترونات الرابطة ثم طرح القيمة التي تم الحصول عليها،من عدد إلكترونات التكافؤ. مجموع جميع الشحنات الرسمية في جزيء أو أيون،يساوي صافي شحنة الجزيء أو الأيون.على سبيل المثال،يمكن تمثيل أكسيد النيتروز بثلاثة بنيات لويس محتملة واحدة مع رابطتين ثنائيتين،واحدة مع رابطة ثلاثية بين ذرات النيتروجين،وواحدة مع رابطة ثلاثية بين النيتروجين والأكسجين كل ذلك يكمل الثمانية. تم تحديد أفضل بنية لويس من خلال،حساب الشحنات الرسمية. يحتوي النيتروجين على خمسة إلكترونات تكافؤ،والأكسجين ستة إلكترونات تكافؤ.الحساب المبني على،عدد الإلكترونات غير المترابطة ونصف عدد الإلكترونات الرابطة،يعطي الشحنة الرسمية لكل بنية. لأن أكسيد النيتروز جزيء متعادل،يجب أن يكون مجموع جميع الشحنات الرسمية صفرًا. بشكل عام،الشحنات الرسمية على الذرات المفردة في بنية لويس المهيمنة،أقرب إلى الصفر.ومن ثم،البنية الثالثة ذات الشحنة الرسمية الأعلى يمكن تجاهلها. بالإضافة إلى ذلك،الشحنة الرسمية السلبية،إن وجد،يجب أن يتم حملها،بواسطة أكثر الذرات سالبيةكهربية. بما أن الأكسجين أكثر سالبيةكهربية من النيتروجين،البنية الثانية،ذات الشحنة الرسمية السلبية على الأكسجين،يتم تحديدها على أنها البنية المهيمنة لأكسيد النيتروز.الشحنات الرسمية ليست الشحنات الفعلية للجزيئات أو الذرات،ولكن اتفاقية مسك الدفاتر. الشحنة الفعلية للجزيء تعتمد على عدة عوامل،بما في ذلك الفرق في السالبيةالكهربية بين الذرات المكونة.

الشحنات الرسمية

في بعض الحالات، يبدو أن هناك أكثر من بنية لويس صالحة للجزيئات والأيونات متعددة الذرات. يمكن استخدام مفهوم الرسوم الرسمية للمساعدة في توقع هيكل لويس الأكثر ملاءمة عند وجود أكثر من هيكل معقول. <h4> حساب الشحنات الرسمية </h4> الشحنة الرسمية للذرة في الجزيء هي الشحنة الافتراضية للذرة إذا كانت الإلكترونات في الروابط موزعة بالتساوي بين الذرات. بدلاً من ذلك، تنتج الشحنة الرسمية من عدد إلكترونات التكافؤ للذرة المحايدة، يتم أولاً تقليل الإلكترونات غير المترابطة، متبوعاً بطرح عدد الروابط المتصلة بتلك الذرة في بنية لويس. وبالتالي، يتم احتساب الرسوم الرسمية على النحو التالي:  <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/1065/1065_Equations-01.png" style="height: 60px;" /> يمكن إعادة التحقق من حسابات الشحنات الرسمية من خلال تحديد مجموع الشحنات الرسمية للهيكل بأكمله. يجب أن يكون مجموع الشحنات الرسمية لجميع الذرات في الجزيء صفراً ؛ يجب أن يساوي مجموع الشحنات الرسمية في أيون شحنة الأيون. تذكر أن الشحنة الرسمية المحسوبة للذرة ليست الشحنة الفعلية للذرة في الجزيء. الشحنة الرسمي هو مجرد إجراء مفيد لمسك الدفاتر؛ لا يشير إلى وجود شحنات فعلية. <h4> حساب الرسوم الرسمية من هياكل لويس </h4> يتم اتباع الخطوات التالية لتعيين شحنات رسمية لكل ذرة في ICl4−.الخطوة 1. قسّم أزواج الإلكترون الرابطة بالتساوي لجميع روابط I–Cl : <img alt="Figure1" src="https://www.jovecore.com/CDNSource/lessons/1065/1065image_1.svg" style="height: 120px;" />الخطوة الثانية. قم بتعيين أزواج وحيدة من الإلكترونات لذراتهم. كل ذرة كلور لديها الآن سبعة إلكترونات مخصصة لها، ولذرة اليود ثمانية. الخطوة 3. اطرح هذا الرقم من عدد إلكترونات التكافؤ للذرة المحايدة: اليود: 7 – 8 = –1 الكلور: 7 – 7 = 0 مجموع الشحنات الرسمية لجميع الذرات يساوي –1 ، وهو مطابق لشحنة الأيون (–1). <h4> استخدام الشحنة الرسمية للتنبؤ بالهيكل الجزيئي </h4> يسمى ترتيب الذرات في جزيء أو أيون هيكلها الجزيئي. في كثير من الحالات ، قد يؤدي اتباع الخطوات لكتابة هياكل لويس إلى أكثر من بنية — جزيئية محتملة وروابط مختلفة متعدّدة ومواضع إلكترون أحادية الزوج أو ترتيبات مختلفة من الذرات، على سبيل المثال. يمكن أن تساعد بعض الإرشادات التي تتضمن الشحنة الرسمية في تحديد الهياكل المحتملة الأكثر احتمالاً لجزيء أو أيون معين: <ol><li> يُفضل التركيب الجزيئي الذي تكون فيه جميع الشحنات الرسمية صفرًا على البنية التي لا تكون فيها بعض الشحنات الرسمية صفرية. </li><li> إذا كان يجب أن يتضمن هيكل لويس شحنات رسمية غير صفرية ، يفضل الترتيب مع أصغر شحنات رسمية غير صفرية. </li><li> يُفضل استخدام هياكل لويس عندما تكون الشحنات الرسمية المجاورة صفراً أو بعلامة معاكسة. </li><li> عند الاختيار من بين العديد من هياكل لويس ذات التوزيعات المتشابهة للشحنات الشكلية ، يفضل استخدام البنية ذات الشحنات الشكلية السالبة على الذرات الأكثر كهربيًا.</ol>
 
 p> لمعرفة كيفية تطبيق هذه الإرشادات، ضع في اعتبارك بعض الهياكل المحتملة لثاني أكسيد الكربون ، CO2. من المعروف أن الذرة الأقل كهرسلبية تشغل عادةً الموقع المركزي، لكن الرسوم الرسمية تساعد في فهم سبب حدوث ذلك. يمكن استخلاص ثلاثة احتمالات للهيكل: الكربون في المركز مع رابطتين مزدوجتين، والكربون في المركز برابطة فردية وثلاثية، والأكسجين في المركز مع روابط مزدوجة. <img alt="Figure2" src="https://www.jovecore.com/CDNSource/lessons/1065/1065image_2.svg" style="height: 80px;" /> عند مقارنة الرسوم الرسمية الثلاثة، يمكن تحديد الهيكل الموجود على اليسار على أنه مفضل لأنه يحتوي على رسوم رسمية فقط بقيمة صفر. كمثال آخر، يمكن أن يحتوي أيون الثيوسيانات، وهو أيون يتكون من ذرة كربون وذرة نيتروجين وذرة كبريت، على ثلاثة تركيبات جزيئية مختلفة: NCS–, CNS–, أو CSN–. يمكن أن تساعد الشحنات الرسمية الموجودة في كل من هذه الهياكل الجزيئية في اختيار الترتيب الأكثر احتمالًا للذرات. هياكل لويس المحتملة والشحنات الرسمية لكل من الهياكل الثلاثة المحتملة لأيون الثيوسيانات هي - الكربون في المركز مع الروابط المزدوجة، والنيتروجين في المركز مع الروابط المزدوجة، والكبريت في المركز مع الروابط المزدوجة. & nbsp ؛ <img alt="Figure3" src="https://www.jovecore.com/CDNSource/lessons/1065/1065Image_3.svg" style="height: 95px;" /> لاحظ أن مجموع الرسوم الرسمية في كل حالة يساوي شحنة الأيون (–1). ومع ذلك، يفضل الترتيب الأول للذرات مع الكربون في المركز لأنه يحتوي على أقل عدد من الذرات ذات الشحنات الرسمية غير الصفرية. كما أنه يضع أقل ذرة كهربية في المركز والشحنة السالبة على العنصر الأكثر كهرسلبية. هذا النص مقتبس من <a href="https://openstax.org/books/chemistry-2e/pages/7-4-formal-charges-and-resonance">Openstax, Chemistry 2e, Chapter 7.4 Formal Charges and Resonance.</a>

في بعض الحالات ، يبدو أن هناك أكثر من هيكل لويس صالح للجزيئات والأيونات متعددة الذرات. يمكن استخدام مفهوم الرسوم الرسمية ل ...

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lewis structures with formal charge

Lewis structures can sometimes show more than one reasonable arrangement for a molecule or polyatomic ion. Formal charge helps chemists choose the best Lewis structure when that happens. It is a useful way to compare possible structures in chemistry.

Formal charge is the hypothetical charge an atom would have if bonding electrons were shared evenly between the atoms. It can also be found by starting with the valence electrons of the neutral atom, subtracting the nonbonding electrons, and then subtracting the number of bonds on that atom in the Lewis structure. This is a bookkeeping tool, not the actual charge on the atom.

The formal charge of a full structure should also be checked as a whole. For a neutral molecule, the sum of all formal charges must be zero. For an ion, the sum of all formal charges should match the ion’s overall charge.

A common example is the interhalogen ion ICl4−. To assign formal charges, the bonding electron pairs are divided equally among the I–Cl bonds. Then lone pairs are assigned to their atoms. In this structure, each chlorine has seven electrons assigned to it, and iodine has eight. That gives iodine a formal charge of −1 and each chlorine a formal charge of 0, which adds up to the −1 charge of the ion.

Formal charge also helps predict molecular structure when several Lewis structures are possible. A structure with all formal charges equal to zero is preferred over one with nonzero charges. If nonzero charges are needed, the best choice has the smallest charges possible. Structures are also preferred when adjacent formal charges are zero or opposite in sign. When several choices are still possible, the negative charge should be on the more electronegative atom.

Carbon dioxide shows why these rules matter. One possible structure has carbon in the center with two double bonds. Other possibilities place carbon between a single and a triple bond, or place oxygen in the center with double bonds. The structure with carbon in the center and two double bonds is preferred because all of its formal charges are zero.

The thiocyanate ion, NCS−, gives another clear example. It can be written with carbon, nitrogen, or sulfur in the center. The formal charges in each possible Lewis structure help identify the most likely arrangement of atoms. The carbon-centered structure is preferred because it has the fewest atoms with nonzero formal charges. It also places the least electronegative atom in the center and the negative charge on the more electronegative element.

Lewis Structures with Formal Charge

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formal charges

Lewis structures can sometimes show more than one reasonable arrangement for a molecule or polyatomic ion. Formal charge helps chemists choose the best Lewis structure when that happens. It is a useful way to compare possible structures in chemistry. Formal charge is the hypothetical charge an atom would have if bonding electrons were shared evenly between the atoms. It can also be found by starting with the valence electrons of the neutral atom, subtracting the nonbonding electrons, and then...

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Learn how formal charge helps compare Lewis structures, check total charge, and choose the best arrangement for molecules and ions like CO2 and NCS−.

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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 ...

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

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 ...

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.

molecular-comparison-of-gases-liquids-and-solids

Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions ...

comparing-intermolecular-forces-melting-point-boiling-point

Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

Construct an explanation to summarize the influences intermolecular forces have on the properties of chemical compounds.

PS.Chm.3.2

Analyze the structure of atoms and isotopes.

Lewis Structures with Formal Charge

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