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

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.3.1

The Born-Haber Cycle

יצירת קשרים יוניים מחייבת העברת אלקטרונים מאטום מתכת לאטום של אל-מתכת, תהליך שלעיתים קרובות הוא אנדותרמי. אך כאשר היסודות נתרן וכלור מגיבים זה עם זה ליצירת גביש נתרן כלורי מוצק, זהו תהליך אקסותרמי ביותר. אבל מאיפה האנרגיה?על פי חוק קולון, קטיונים ואניונים נמשכים זה לזה על ידי כוחות אלקטרוסטטיים חזקים ויוצרים מערך מוצק, או סריג. מבנה הסריג הנוצר מתייצב על ידי הקטנת האנרגיה הפוטנציאלית, המשתחררת כחום, תגובה אקסותרמית. האנרגיה הכוללת הקשורה להיווצרות או לפירוק של סריג גבישי למרכיביו הגזיים נקראת אנרגיית סריג"בתרכובת יונית מוצקה, מספר גדול של חלקיקים טעונים נמצאים באינטראקציה זה עם זה, מה שמקשה להוכיח את הערך המדויק של אנרגיית הסריג באמצעות ניסוי.יחד עם זאת, ניתן לחשב את האנרגיה על פי חוק הס בסדרת שלבים היפותטיים הנקראים מעגל בורן-הבר"המתארת היווצרות של תרכובת יונית מהיסודות המרכיבים אותה. לדוגמה, מעגל בורן-הבר להיווצרות נתרן כלורי לוקח בחשבון שני מסלולים חלופיים, אחד ישיר והשני עקיף. המסלול הישיר מייצג את האנתלפיה הסטנדרטית של היווצרות NaCl מהיסודות נתרן וכלור.המסלול העקיף כולל חמישה שלבים. בשלב הראשון, נתרן במצב צבירה מוצק מומר לצורתו הגזית. לאחר מכן, מולקולות כלור דיאטומיות מתנתקות לאטומי כלור גזיים.בשלב השלישי והרביעי, אלקטרון מועבר ונוצרים יונים. אלקטרון נגרע מהנתרן הגזי כדי ליצור קטיון נתרן. האלקטרון נוסף לכלור הגזי ונוצר אניון כלורי.בשלב האחרון, המשיכה האלקטרוסטטית בין היונים הגזיים מובילה להיווצרות של מבנה הסריג. חוק הס קובע כי השינוי באנתלפיה הכוללת של תהליך המתרחש בשלבים הוא סכום שינויי האנתלפיה של כל שלב. כלומר, ערך האנתלפיה של המסלול הישיר שווה לסכום האנתלפיות של חמשת השלבים.על ידי פתרון המשוואה של אנרגיית הסריג נקבע ערך שלילי גדול, שמבטא תגובה אקסותרמית.

תהליך המחזור של בורן-הבר

<div style="direction:rtl">
 	
 	<h4>אנרגיית סריג</h4> 

 	תרכובת יונית יציבה בגלל המשיכה האלקטרוסטטית בין היונים החיוביים והשליליים שלה. אנרגיית הסריג של תרכובת היא מדד לחוזקה של משיכה זו. אנרגיית הסריג (ΔHlattice) של תרכובת יונית מוגדרת כאנרגיה הנדרשת להפרדת מול אחד של המוצק ליונים הגזים המרכיבים אותו. 

 	כאן, נעשה שימוש במוסכמה שבה המוצק היוני מופרד ליונים, כלומר אנרגיות הסריג יהיו אנדותרמיות (ערכים חיוביים). דרך נוספת היא להשתמש במוסכמה מקבילה אך הפוכה, שבה אנרגיית הסריג היא אקסותרמית (ערכים שליליים) ומתוארת כאנרגיה המשתחררת כאשר יונים מתאחדים ליצירת סריג. לפיכך, הקפד לאשר באיזו הגדרה נעשה שימוש בעת חיפוש אנרגיות סריג בהתייחסות אחרת. 

 	בשני המקרים, גודל גדול יותר עבור אנרגיית הסריג מצביע על תרכובת יונית יציבה יותר. עבור נתרן כלורי, ΔHlattice = 769 קילו-ג'ול. לפיכך, זה דורש 769 קילו-ג'ול כדי להפריד מול אחד של NaCl מוצק ליוני Na+ ו- Cl– גזיים. כאשר מול אחד של יוני Na+ ו- Cl– גזי יוצרים NaCl מוצק, 769 קילו-ג'ול של חום משתחרר. 

 	<h4>קביעת אנרגיית הסריג של תרכובת יונית</h4> 

 	לא ניתן למדוד אנרגיות סריג ישירות. עם זאת, ניתן לחשב את אנרגיית הסריג באמצעות מחזור תרמוכימי. מחזור בורן-הבר הוא יישום של חוק ההס שמפרק את היווצרותו של מוצק יוני לסדרה של שלבים בודדים: 

 	<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;">Enthalpy of sublimation of Cs (s)</td> <td colspan="2" style="color: black; border: 1px solid black; text-align: center;">Cs (s) → Cs (g)</td> 
 				<td style="color: black; border: 1px solid black; text-align: center;">ΔH = ΔHs° = 76.5 kJ/mol</td> </tr> 

 			<tr> 


 				<td style="color: black; border: 1px solid black; text-align: center;">One-half of the bond energy of F2</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;">Ionization energy of Cs (g)</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;">Electron affinity of F</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;">Negative of the lattice energy of CsF (s)</td> 
 			<td colspan="2" style="color: black; border: 1px solid black; text-align: center;">Cs+ (g) + F− (g) → CsF (s)</td> 
 			<td style="color: black; border: 1px solid black; text-align: center;">ΔH = −ΔHlattice = ?</td> </tr> 

 		<tr> 
 			<td style="color: black; border: 1px solid black; text-align: center;">Enthalpy of formation of CsF (s), add steps 1–5</td> 
 			<td colspan="2" style="color: black; border: 1px solid black; text-align: center;">ΔH = ΔHf° = ΔHs°+ ½ D + IE + (EA) + (−ΔHlattice) Cs (s) + ½ F2 (g) → CsF (s)</td> 

 			<td style="color: black; border: 1px solid black; text-align: center;">ΔH = −553.5 kJ/mol</td> </tr> 
 		</tbody> </table> 

 		<ol style="padding-right: 35px; margin: 0;"> 
			<li style="text-align: right;">שקול את היסודות במצבים הנפוצים ביותר שלהם, Cs (s) ו-F2 (g).</li> 
			<li style="text-align: right;">ה- ΔHs° מייצג את ההמרה של צסיום מוצק לגז (סובלימציה), ואז אנרגיית היינון הופכת את אטומי הצסיום הגזיים לקטיונים.</li> 
			<li style="text-align: right;">בשלב הבא, יש להתייחס לאנרגיה הדרושה כדי לשבור את הקשר F–F לייצור אטומי פלואור.</li> 
			<li style="text-align: right;">המרת מול אחת של אטומי פלואור ליוני פלואוריד היא תהליך אקסותרמי, ולכן שלב זה מפיץ אנרגיה (זיקת האלקטרונים)</li> 
			<li style="text-align: right;">כעת, קיימת מול אחת של קטיוני Cs ומול אחת של אניוני F. יונים אלה מתאחדים לייצור פלואוריד צסיום מוצק. שינוי האנתלפיה בשלב זה הוא השלילי של אנרגיית הסריג, כך שזו גם כמות אקסותרמית.</li> 
			<li style="text-align: right;">סך האנרגיה המעורבת בהמרה זו שווה לאנתלפיה של היווצרות שנקבעה בניסוי, ΔHf°, של התרכובת מהיסודות שלה. במקרה זה, השינוי הכולל הוא אקסותרמי.</li> 
		</ol> 

 	אנרגיות הסריג המחושבות עבור תרכובות יוניות הן בדרך כלל גבוהות בהרבה מאנרגיות פירוק הקשר הנמדדות עבור קשרים קוולנטיים. בעוד שאנרגיות הסריג נופלות בדרך כלל בטווח של 600 - 4000 קילו ג'ול/מול (חלקן אפילו גבוהות יותר), אנרגיות ניתוק הקשרים הקוולנטיים הן בדרך כלל בין 150 - 400 קילו ג'ול/מול עבור קשרים בודדים. עם זאת, זכור שלא מדובר בערכים הניתנים להשוואה ישירות. עבור תרכובות יוניות, אנרגיות הסריג קשורות לאינטרקציות רבות, שכן קטיונים ואניונים נאספים יחד בסריג מורחב. עבור קשרים קוולנטיים, אנרגיית פירוק הקשר קשורה לאינטרקציה של שני אטומים בלבד. 

 	<h4>אנרגיית סריג כפונקציה של רדיוס יונים ומטען</h4> 

 	אנרגיית הסריג של קריסטל יוני גדלה במהירות ככל שמטענים של היונים גדלים, וגדלים של היונים יורדים. כאשר כל שאר הפרמטרים נשמרים קבועים, הכפלת המטען של הקטיון והאניון מכפילה פי ארבעה את אנרגיית הסריג. לדוגמה, אנרגיית הסריג של LiF (Z+ ו-Z– = 1) היא 1023 קילו-ג'ול/מול, ואילו זו של MgO (Z+ ו-Z- = 2) היא 3900 קילו-ג'ול/מול (Ro = המרחק האינטריוני המוגדר כסכום של הרדיוסים של היונים החיוביים והשליליים, כמעט זהים - בערך 200 pm עבור שתי התרכובות).
 	
 	מרחקים בין-אטומיים שונים מייצרים אנרגיות סריג שונות. לדוגמה, השווה את אנרגיית הסריג של MgF2 (2957 קילו-ג'ול/מול) לזו של MgI2 (2327 קילו-ג'ול-מול), מה שמדגים את ההשפעה על אנרגיית הסריג של הגודל היוני הקטן יותר של F– בהשוואה ל-I–.

 	<h4>יישומים אחרים של תהליך מחזור של בורן-הבר</h4> 

 	ניתן להשתמש במחזור בורן-הבר גם כדי לחשב כל אחת מהכמויות האחרות במשוואה עבור אנרגיית הסריג, בתנאי שהשאר ידוע. לדוגמה, אם ידועה האנתלפיה הרלוונטית של סובלימציה ΔHs°, אנרגיית יינון (IE), אנתלפיית פירוק קשר (D), אנרגיית הסריג ΔHlattice ואנתלפיה סטנדרטית של היווצרות ΔHf°, ניתן להשתמש במחזור בורן-הבר כדי לקבוע את הזיקה האלקטרונית של האטום. 

 	טקסט זה מותאם מ <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></div>

אנרגיית סריג

תרכובת יונית היא יציבה בגלל המשיכה האלקטרוסטטית בין היונים החיוביים והשליליים שלה. אנרגיית הסריג של ...

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Chemical Bonding: Basic Concepts

קשרים כימיים: מושגים בסיסיים

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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

predicting-ionic-stability-with-lattice-energy

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...

lewis symbols and the octet rule

Valence Electrons, Lewis Symbols, and Bonding

Chemical bonds form when atoms or ions interact in ways that lower the potential energy of a molecule. Gilbert N. Lewis created a simple model to show bond formation using valence electrons, the electrons in the outer shell. In this model, electrons are shared or transferred to help atoms reach a stable electron configuration. The Lewis model helps describe two common bond types. An ionic bond forms when electrons move from a metal to a nonmetal. A covalent bond forms when two nonmetals share...

electronegativity

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...

ionic bonding and electron transfer

Ionic Compounds and Crystal Lattices

Ionic compounds form when positive and negative ions attract each other. A cation is a positive ion, and it forms when an atom loses one or more valence electrons. An anion is a negative ion, and it forms when an atom gains one or more valence electrons. Compounds made of these ions are called ionic compounds, or salts, and the force between them is an ionic bond. The properties of ionic solids help show how strong this attraction is. They usually form rigid, brittle crystals and have high...

trends in lattice energy: ion size and charge

trends-in-lattice-energy-ion-size-and-charge

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

Shared Electrons in Covalent Molecules

Covalent molecules form when atoms share electrons instead of transferring them. This bonding usually happens between nonmetal atoms with similar tendencies to attract electrons. Because the atoms pull on the electrons in a shared way, the bond is held together by mutual attraction. Covalent compounds often have physical properties that differ from ionic compounds. The attraction between neutral molecules is weaker than the attraction between charged ions. As a result, many covalent compounds...

bond polarity, dipole moment, and percent ionic character

bond-polarity-dipole-moment-and-percent-ionic-character

How Bond Polarity Shapes Molecular Dipoles

Bond polarity depends on electronegativity, the ability of an atom to attract shared electrons. The absolute value of the electronegativity difference, or ΔEN, gives a rough guide to bond type. When the difference is very small or zero, the bond is covalent and nonpolar. When it is larger, the bond may be polar covalent or ionic. Examples show how this works in real compounds. H–H has a ΔEN of 0, so it is nonpolar. H–Cl has a ΔEN of 0.9, so it is polar covalent. Na–Cl has a ΔEN of 2.1, so it...

lewis structures of molecular compounds and polyatomic ions

lewis-structures-of-molecular-compounds-and-polyatomic-ions

Drawing Lewis Structures with Valence Electron Counts

Drawing Lewis structures starts with counting valence electrons and building the atom arrangement step by step. Valence electrons are the outer-shell electrons that help show how atoms bond. For ions, a positive charge means one electron is removed for each plus sign, and a negative charge means one electron is added for each minus sign. The next step is to sketch the skeleton structure. The least electronegative atom usually goes in the center, while hydrogen is almost never central. Fluorine...

resonance

Resonance Forms in Lewis Structures

Resonance forms in Lewis structures help explain molecules and ions that cannot be shown correctly with just one drawing. In nitrite ion, NO2−, the Lewis structure can be drawn in two ways. The N-O and N=O bonds switch positions in the two drawings, but the atoms stay in the same arrangement. If nitrite really had one single bond and one double bond, the two bond lengths should be different. A double bond is shorter and stronger than a single bond between the same atoms. Experiments show that...

formal charges

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...

exceptions to the octet rule

Octet Rule Exceptions in Lewis Structures

Some covalent molecules do not follow the octet rule in their Lewis structures. Their central atoms can fall into three groups: odd-electron molecules, electron-deficient molecules, and hypervalent molecules. These cases show why a Lewis structure may not always give every atom eight valence electrons. Odd-electron molecules have an odd number of valence electrons, so one electron remains unpaired. Molecules with an odd number of electrons are called radicals. Nitric oxide, NO, is one example,...

bond energies and bond lengths

How Bond Energy Predicts Reaction Heat

Bond energy helps explain why molecules stay together and how much heat a reaction may release or absorb. A covalent bond is stronger when more energy is needed to separate the atoms. The energy needed to break one specific covalent bond in one mole of gaseous molecules is called bond energy, or bond dissociation energy. For a diatomic molecule, bond energy is the standard enthalpy change for an endothermic reaction that breaks that bond. The H-H bond is a common example. Its bond energy is...

bonding in metals

Electron Sea Model in Metals

Electron sea model explains how metallic bonding holds metals together. In this model, most metal atoms do not have enough valence electrons to form ionic or covalent bonds in the usual way. Their valence electrons are held loosely because metals have low electronegativity, and their ionization energy is low, so electrons are removed easily. When a metal atom loses these outer electrons, it becomes a positively charged metal ion. The freed electrons form a delocalized electron cloud around...

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

chemistry

JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

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Ohio’s Learning Standards and Model Curriculum

Structure And Properties Of Matter

Chemical bonding

Tennessee Academic Standards

High School

Matter and Its Interactions

CHEM1.PS1.14

Virginia  Standards of Learning

HIgh School

CH.3

CH.3.d

Physics

PH.9

PH.9.e

Alabama Course of Study Science

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Motion and Stability: Forces and Interactions

9-12.C.2.2.b

Texas Essential Knowledge and Skills

Chemistry and Physics

IPC.7

IPC.7.A

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New York State Science Learning Standards

Physical Science

HS. Structure and Properties of Matter

HS-PS1-3.

HS. Chemical Reactions

HS-PS1-2.

Georgia Standards of Excellence

SC2.

bonding-types-from-nonpolar-covalent-to-ionic

Bonding Types: From Nonpolar Covalent to Ionic

Scientific Laws and Theories

Scientific Laws

In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. ...

The Scientific Method

Chemistry is an empirical science. Scientists often pose questions to understand the chemistry in everyday life and seek answers to these questions. To ...

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Use models to explain how the scientific understanding of atomic structure has evolved.

PS.Chm.1.1

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10&#8722;15 meters, a nucleus is ...

Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

electron-configuration-of-multielectron-atoms

Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

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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