The resulting compounds are called ionic compounds and are the primary subject of this section. Y o u w i l l n e e d t o d e t e r m i n e h o w m a n y o f e a c h i o n y o u w i l l n e e d t o f o r m a n e u t r a l f o r m u l a u n i t ( c o m p o u n d ) C a t i o n L D S A n i o n L D S A l g e b r a f o r n e u t r a l c o m p o u n d I O N I C C O M P O U N D L D S N a + C l N a " ( [ N a ] + C l ( [ C l ] % ( + 1 ) + ( - 1 ) = 0 [ N a ] + [ C l ] % K + F M g + I B e + S N a + O G a + S R b + N W K S 6 . We have already encountered some chemical . % If there is a prefix, then the prefix indicates how many of that element is in the compound. The rules for organic compounds, in which carbon is the principle element, will be treated in a later chapter on organic chemistry. Ionic compounds are produced when a metal bonds with a nonmetal. The \(H^\circ_\ce s\) represents the conversion of solid cesium into a gas, and then the ionization energy converts the gaseous cesium atoms into cations. Chemical bonding is the process of atoms combining to form new substances. Mg + I 3. An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. Chapter 2: Chemical Compounds and Bonding Section 2.1: Ionic Compounds, pages 22 23 1. Thus, in calculating enthalpies in this manner, it is important that we consider the bonding in all reactants and products. 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The Molecular Formula for Water. Draw Lewis dot structures for each of the following atoms: Determine the common oxidation number (charge) for each of the following ions, and then draw their. Every day you encounter and use a large number of ionic compounds. a. ionic b. binary . An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. Since Xe has an atomic number of 54, which is much greater than 14, we can break the octet rule and add the necessary number of electrons to Xe. Count the valence electrons present so far. Because D values are typically averages for one type of bond in many different molecules, this calculation provides a rough estimate, not an exact value, for the enthalpy of reaction. In this section, you will learn about the bond strength of covalent bonds, and then compare that to the strength of ionic bonds, which is related to the lattice energy of a compound. Aluminum ion Silicon ionPotassium ionFluoride ion Sulfide ionCarbide ionHydrogen ion Cesium ionBromide ionChloride ion Gallium ionZinc ionSilver ion Oxide ion Barium ion Predict the common oxidation numbers (CHARGE) for each of the following elements when they form ions. What are the three kinds of bonds which can form between atoms? Draw brackets around the lewis dot structures of the cation and anion and draw the charges outside of the brackets. WKS 6.3 - LDS for Ionic Compounds (2 pages) Fill in the chart below. Dont forget to balance out the charge on the ionic compounds. For example, the bond energy of the pure covalent HH bond, \(\Delta_{HH}\), is 436 kJ per mole of HH bonds broken: \[H_{2(g)}2H_{(g)} \;\;\; D_{HH}=H=436kJ \label{EQ2} \]. Lewis structures serve as one of the most important topics in this unit and the course as a whole, with the ability to draw out any molecule opening the door to thousands of other possibilities. Since the compound has a charge, we would just have to take one electron away. 3.5: Ionic Compounds- Formulas and Names is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts. One property common to metals is ductility. REMEMBER: include brackets with a charge for . cyanide ion bromide ionsulfur dioxide SO2 ammonium phosphate sulfur hexafluoride SF6 bromine pentachloride BrCl5chlorate ion carbon monoxide CO carbonate ion chlorine tribromide ClBr3 WKS 6.6 VSEPR Shapes of Molecules (2 pages) Predict the AByXz and molecular shape of each of the following. If the compound is molecular, does it contain hydrogen? Indicate whether the following statements are true (T) or false (F). We saw this in the formation of NaCl. Monatomic ions are formed from single atoms that have gained or lost electrons. Binary acids are named using the prefix hydro-, changing the ide suffix to ic, and adding acid; HCl is hydrochloric acid. Stable molecules exist because covalent bonds hold the atoms together. First, is the compound ionic or molecular? This accounts for a total of 16 valence electrons since the carbon atom has four and each of the two sulfur atoms have six. The O2 ion is smaller than the Se2 ion. It is not hard to see this: 70% of our body mass is water and about 70% of the surface, Name: Chemistry Post-Enrolment Worksheet The purpose of this worksheet is to get you to recap some of the fundamental concepts that you studied at GCSE and introduce some of the concepts that will be part, Chemistry Diagnostic Questions Answer these 40 multiple choice questions and then check your answers, located at the end of this document. The strength of a bond between two atoms increases as the number of electron pairs in the bond increases. We measure the strength of a covalent bond by the energy required to break it, that is, the energy necessary to separate the bonded atoms. It has many uses in industry, and it is the alcohol contained in alcoholic beverages. CHAPTER 6 Chemical Bonding SECTION 1 Introduction to Chemical Bonding OBJECTIVES 1. Explain the difference between metallic, ionic, and covalent bonding Metallic cations share a sea of electrons Ionic atoms give and take electrons. Solid calcium sulfite is heated in a vacuum. When. Some atoms have an odd number of valence electrons, so they would not be able to neatly fit into the octet rule. Page 4 of 10 WKS 6.3 - LDS for Ionic Compounds (continued) Draw just the final Lewis dot structure for each of the following IONIC compounds. Therefore, there is a total of 22 valence electrons in this compound. WRITING CHEMICAL FORMULA For ionic compounds, the chemical formula must be worked out. Predict the common oxidation numbers (CHARGE) for each of the following elements when they form. The precious gem ruby is aluminum oxide, Al2O3, containing traces of Cr3+. WKS 6.5 - LDS for All Kinds of Compounds! This means it has six valence electrons and since there are two oxygen atoms, there should be 12 valence electrons in this diagram in total. The attraction between oppositely charged ions is called an ionic bond, and it is one of the main types of chemical bonds in chemistry. Here is what you should be thinking as you get used to drawing these: Looking at the periodic table, we can notice that oxygen is in group 16. In these two ionic compounds, the charges Z+ and Z are the same, so the difference in lattice energy will mainly depend upon Ro. For example, the compound CO2 is represented as a carbon atom joined to two oxygen atoms by double bonds. Phosphorus, CHAPTER 12: CHEMICAL BONDING Active Learning Questions: 3-9, 11-19, 21-22 End-of-Chapter Problems: 1-36, 41-59, 60(a,b), 61(b,d), 62(a,b), 64-77, 79-89, 92-101, 106-109, 112, 115-119 An American chemist, 1. We begin with the elements in their most common states, Cs(s) and F2(g). CHEMISTRY BONDING REVIEW 1. You would remember that Na has 1 valence electron and Br has 7 valence electrons. Ionic compounds are solids that typically melt at high temperatures and boil at even higher temperatures. The energy required to break a specific covalent bond in one mole of gaseous molecules is called the bond energy or the bond dissociation energy. Because the total number of positive charges in each compound must equal the total number of negative charges, the positive ions must be Fe3+, Cu2+, Ga3+, Cr4+, and Ti3+. People also ask Chemical Bonding and Compound Formation Chemical Bonding 7. Which are metals? For cesium chloride, using this data, the lattice energy is: \[H_\ce{lattice}=\mathrm{(411+109+122+496+368)\:kJ=770\:kJ} \nonumber \]. How would the lattice energy of ZnO compare to that of NaCl? Different interatomic distances produce different lattice energies. For example, sodium chloride melts at 801 C and boils at 1413 C. Calcium bromide Aluminum bromideMagnesium oxide Rubidium nitrideAluminum selenide Cesium sulfideStrontium phosphide Beryllium nitridePotassium iodide Lithium silicide WKS 6.4 LDS for Covalent Compounds and Polyatomic Ions (1 page) Covalent molecules are named using prefixes. Valence electrons are in the innermost energy level. Unit 1: Lesson 3. Draw the outside atoms and put single bonds connecting atoms together. Because opposite charges attract (while like charges repel), cations and anions attract each other, forming ionic bonds. 2. WKS 6.3 - LDS for Ionic Compounds (2 pages), Fill in the chart below. Lewis diagrams, or Lewis structures, are a way of drawing molecular structures and showing the present valence electrons and bonds. Chapter 2__Atoms Molecules and Ions_lecture note_student.docx, Mirpur University of Science and Technology, AJ&K, Kami Export - John Myers - 2. Separating any pair of bonded atoms requires energy; the stronger a bond, the greater the energy required to break it. Covalent bonds are a little more difficult to draw out because the electrons are shared. Thus, if you are looking up lattice energies in another reference, be certain to check which definition is being used. There CAN be exceptions to the rules, so be careful when drawing Lewis dot structures. Table 4.5. The Li + ion is more stable because, Source: https://docplayer.net/55440383-Wks-classifying-ionic-versus-covalent-lewis-dot-structures-of-atoms.html, What Directory Should I Upload My Files to Godaddy, Wks 6 3 Lds for Ionic Compounds Continued Answers, Professional Bowler Who Shot a Strike but Pin Came Back Up, High School Getting to Know You Questions, Hiroshima After Iraq Three Studies in Art and War, what are the disadvantages to using solar energy, What Parts of a Chicken Is H=chicken Nuggests Made Up of, Small pieces of deboned, breaded, and bat. One atom in the bond has a partial positive charge, while the other atom has a partial negative charge. Draw the Lewis Dot Structure and formula for MgF. The bond energy is obtained from a table and will depend on whether the particular bond is a single, double, or triple bond. The 415 kJ/mol value is the average, not the exact value required to break any one bond. is associated with the stability of the noble gases. Try drawing the lewis dot structure of the polyatomic ion NH4+. We only need 10 though since each nitrogen atom has five valence electrons, so we have to form double or triple bonds. Common polyatomic ions. This represents the formula SnF2, which is more properly named tin(II) fluoride. Some of these compounds, where they are found, and what they are used for are listed in Table. Name Date Block 2. Look at the empirical formula and count the number of valence electrons there should be total. endobj IDENTIFY each first as being a simple ion, polyatomic ion, ionic compound (with or without a polyatomic ion), or covalent compound. Most of the transition metals can form two or more cations with different charges. The lattice energy of a compound is a measure of the strength of this attraction. A(n) __________________________ bond is a bond in which one atom donates electrons to another atom. Calcium bromide 8. Ionic Compounds. Metallic bonds are ____________________________________ thus metals are able to be pounded into many shapes. The enthalpy change in this step is the negative of the lattice energy, so it is also an exothermic quantity. Magnesium oxide 10. The name of a binary compound containing monatomic ions consists of the name of the cation (the name of the metal) followed by the name of the anion (the name of the nonmetallic element with its ending replaced by the suffix ide). Look at the label or ingredients list on the various products that you use during the next few days, and see if you run into any of those in this table, or find other ionic compounds that you could now name or write as a formula. This can be expressed mathematically in the following way: \[\Delta H=\sum D_{\text{bonds broken}} \sum D_{\text{bonds formed}} \label{EQ3} \]. Given the Lewis electron-dot diagram: boiling point because H 2 O contains stronger metallic bonds covalent bonds ionic bonds hydrogen bonds 2. We can compare this value to the value calculated based on \(H^\circ_\ce f\) data from Appendix G: \[\begin {align*} For example, the sodium ions attract chloride ions and the chloride ion attracts sodium ions. Examples are shown in Table \(\PageIndex{2}\). We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. These charges are used in the names of the metal ions: Write the formulas of the following ionic compounds: (a) CrP; (b) HgS; (c) Mn3(PO4)2; (d) Cu2O; (e) CrF6. Matter in its lowest energy state tends to be more stable. We'll give you the answer at the end! Ionic and molecular compounds are named using somewhat-different methods. The lattice energy () of an ionic compound is defined as the energy required to separate one mole of the solid into its component gaseous ions. 1. Lattice energy increases for ions with higher charges and shorter distances between ions. Try drawing the lewis dot structure of N2. Looking at the periodic table, we know that C has 4 v.e. 2. Since there are 12 total and the octet rule is fulfilled on both atoms, this is the proper lewis dot structure of O2. Then, draw the metals and nonmetals with their respective electrons (you could do this mentally too once you get a hang of this process). Keep in mind, however, that these are not directly comparable values. Molecular Models in Biology Objectives: After this lab a student will be able to: 1) Understand the properties of atoms that give rise to bonds. We will limit our attention here to inorganic compounds, compounds that are composed principally of elements other than carbon, and will follow the nomenclature guidelines proposed by IUPAC. Common Anions Table and Formulas List. **Note: Notice that non-metals get the ide ending to their names when they become an ion. 100. For sodium chloride, Hlattice = 769 kJ. The strength of a covalent bond is measured by its bond dissociation energy, that is, the amount of energy required to break that particular bond in a mole of molecules. Lewis Dot Structure. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. Draw 3 lone pairs on both of the oxygen atoms so that they both have a full octet. This means you need to figure out how many of each ion you need to balance out the charge! In ionic compounds, electrons are completely transferred from one atom to another so that a cationpositively charged ionand an anionnegatively charged ionform. Mg has a +2 charge while Cl has a -1 charge, so the compound is MgCl2. Polyatomic ions formation. The Born-Haber cycle is an application of Hesss law that breaks down the formation of an ionic solid into a series of individual steps: Figure \(\PageIndex{1}\) diagrams the Born-Haber cycle for the formation of solid cesium fluoride. Generally, as the bond strength increases, the bond length decreases. (As a comparison, the molecular compound water melts at 0 C and boils at 100 C.) In solid form, an ionic compound is not electrically conductive because its ions are . CHAPTER 5: MOLECULES AND COMPOUNDS Problems: 1-6, 9-13, 16, 20, 31-40, 43-64, 65 (a,b,c,e), 66(a-d,f), 69(a-d,f), 70(a-e), 71-78, 81-82, 87-96 A compound will display the same properties (e.g. Mg has a +2 charge while Cl has a -1 charge, so the compound is MgCl2. Methanol, CH3OH, may be an excellent alternative fuel. Here are some examples of the first two bullets: Let's go over some relatively straightforward compounds first! <> REMEMBER THE NAMING PATTERN FOR ANIONS - THEY HAVE AN - IDE ENDING! The total energy involved in this conversion is equal to the experimentally determined enthalpy of formation, \(H^\circ_\ce f\), of the compound from its elements. Indicate whether the intermolecular force (IMF) is predominantly H-bonding, Dipole-dipole, or London Dispersion. WKS 6.3 - LDS for Ionic Compounds (continued) Draw just the final Lewis dot structure for each of the following IONIC compounds. The high-temperature reaction of steam and carbon produces a mixture of the gases carbon monoxide, CO, and hydrogen, H2, from which methanol can be produced. Course Hero is not sponsored or endorsed by any college or university. A good example is the ammonium ion made up of one nitrogen atom and four hydrogen atoms. For covalent bonds, the bond dissociation energy is associated with the interaction of just two atoms. An ionic bond is the strongest type of chemical bond, which leads to characteristic properties. Although the four CH bonds are equivalent in the original molecule, they do not each require the same energy to break; once the first bond is broken (which requires 439 kJ/mol), the remaining bonds are easier to break. When the number of protons equals the number of electrons an atom has a _________________________ charge. If you correctly answered less than 25 questions, you need to, Practice Multiple Choice Questions: 1) Which of the following is NOT a laboratory safety rule? nitrite ion nitrogen gas (hint: its diatomic!) A bond in which atoms share electrons is called a _________________________ bond. Define Chemical bond. Once you go through all the steps, you'll notice that there are 14 valence electrons. Binary ionic compounds typically consist of a metal and a nonmetal. Covalent LDS. IDENTIFY each first as being a simple ion, polyatomic ion, ionic compound (with or without a polyatomic ion), or covalent compound. Whereas lattice energies typically fall in the range of 6004000 kJ/mol (some even higher), covalent bond dissociation energies are typically between 150400 kJ/mol for single bonds. ALSO - there may be more than one!!! Transfer valence electrons to the nonmetal (could be done mentally as well). Legal. For example, you cannot have three valence electrons on one side of the xenon atom and three on the other side. Be Study with Quizlet and memorize flashcards containing terms like Is the following sentence true or false? In electron transfer, the number of electrons lost must equal the number of electrons gained. From the answers we derive, we place the compound in an appropriate category and then name it accordingly. The Roman numeral naming convention has wider appeal because many . When compared to H 2 S, H 2 O has a higher 8. 3. The oppositely-charged ions formed, K + and Cl -, are then strongly attracted to each other by strong electrostatic forces in the crystal lattice, called ionic bonds or electrovalent bonds. 3 0 obj Include 2 LDSs as examples. (1 page) Draw the Lewis structure for each of the following. 7. Some examples are given in Table \(\PageIndex{2}\). The lattice energy of a compound is a measure of the strength of this attraction. Ionic Compound Properties. data-quail-id="56" data-mt-width="1071">. The strong electrostatic attraction between adjacent cations and anions is known as an ionic bond. Ionic bonds are caused by electrons transferring from one atom to another. For example, the sum of the four CH bond energies in CH4, 1660 kJ, is equal to the standard enthalpy change of the reaction: The average CH bond energy, \(D_{CH}\), is 1660/4 = 415 kJ/mol because there are four moles of CH bonds broken per mole of the reaction. In electron transfer, the number of electrons lost must equal the number of electrons gained. (1 page) Draw the Lewis structure for each of the following. &=[201.0][110.52+20]\\ Metals transfer electrons to nonmetals. The lattice energy \(H_{lattice}\) of an ionic crystal can be expressed by the following equation (derived from Coulombs law, governing the forces between electric charges): \[H_{lattice}=\dfrac{C(Z^+)(Z^)}{R_o} \label{EQ7} \]. It is not possible to measure lattice energies directly. Thus, FeCl2 is iron(II) chloride and FeCl3 is iron(III) chloride. Chemists use nomenclature rules to clearly name compounds. Correspondingly, making a bond always releases energy. 1 0 obj Hydrogen bonding intermolecular forces are stronger than London Dispersion intermolecular forces. This excess energy is released as heat, so the reaction is exothermic. Covalent Compounds. Dont forget to show brackets and charge on your LDS for ions! The other fluoride of tin is SnF4, which was previously called stannic fluoride but is now named tin(IV) fluoride. Solid calcium carbonate is heated. Both metals and nonmetals get their noble gas configuration. Ionic bonds and ionic compounds<br />Chapter 6.3<br /> 2. Draw two sulfur atoms, connecting them to the carbon atom with a single bond (4 electrons so far out of 16). The most common example of an ionic compound is sodium chloride NaCl . In the next step, we account for the energy required to break the FF bond to produce fluorine atoms. In a(n) ____________________________ bond many electrons are share by many atoms. Naming Ionic Compounds Using -ous and -ic . The following diagram is. ALSO - there may be more than one!!! A bonds strength describes how strongly each atom is joined to another atom, and therefore how much energy is required to break the bond between the two atoms. Note that we are using the convention where the ionic solid is separated into ions, so our lattice energies will be endothermic (positive values). PARTICLELEWIS DOT#POLAR BONDS# NON-POLAR BONDSMOLECULE POLAR?IMFArsenic trichloride AsCl3 Carbon tetrachloride CCl4 Carbon disulfide CS2 Sulfur trioxide SO3 Boron trichloride BCl3 Phosphorus pentachloride PCl5 Nitrogen gas (diatomic!) Although Roman numerals are used to denote the ionic charge of cations, it is still common to see and use the endings -ous or -ic.These endings are added to the Latin name of the element (e.g., stannous/stannic for tin) to represent the ions with lesser or greater charge, respectively. 2: Lewis Dot Symbols for the Elements in Period 2. Paul Flowers (University of North Carolina - Pembroke),Klaus Theopold (University of Delaware) andRichard Langley (Stephen F. Austin State University) with contributing authors. Multiple bonds are stronger than single bonds between the same atoms. Table T2 gives a value for the standard molar enthalpy of formation of HCl(g), \(H^\circ_\ce f\), of 92.307 kJ/mol. ions. Ionic compounds typically exist in the gaseous phase at room temperature. Ionic compounds - neutral charge. Here are a few examples, but we'll go through some more using these steps! For example, CF is 439 kJ/mol, CCl is 330 kJ/mol, and CBr is 275 kJ/mol. Molecular compounds can form compounds with different ratios of their elements, so prefixes are used to specify the numbers of atoms of each element in a molecule of the compound. Calcium bromide 8. Cesium as the, Name period Unit 3 worksheet Read chapter 8, 2.52.7 1. Especially on those pesky non-metals in Groups 14 & 15. melting, NAME 1. Nomenclature of Ionic Compounds Ionic compounds are composed of ions. The attraction between oppositely charged ions is called an ionic bond, and it is one of the main types of chemical bonds in chemistry. The enthalpy change, H, for a chemical reaction is approximately equal to the sum of the energy required to break all bonds in the reactants (energy in, positive sign) plus the energy released when all bonds are formed in the products (energy out, negative sign). Compounds of these metals with nonmetals are named with the same method as compounds in the first category, except the charge of the metal ion is specified by a Roman numeral in parentheses after the name of the metal. Other examples are provided in Table \(\PageIndex{3}\). Download for free at http://cnx.org/contents/85abf193-2bda7ac8df6@9.110). Which, 9 CHEMICAL NAMES AND FORMULAS SECTION 9.1 NAMING IONS (pages 253 258) This section explains the use of the periodic table to determine the charge of an ion. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. H&= \sum D_{bonds\: broken} \sum D_{bonds\: formed}\\ The compound Al2Se3 is used in the fabrication of some semiconductor devices. If you draw a double bond, you'd still notice that we don't have 14 valence electrons, so there should be a triple bond. The number of atoms in a mole of any pure substance, Ionic and Metallic Bonding BNDING AND INTERACTINS 71 Ions For students using the Foundation edition, assign problems 1, 3 5, 7 12, 14, 15, 18 20 Essential Understanding Ions form when atoms gain or lose, Oxidation States of Nitrogen HNO 3 NH 3 HNO 2 NO N 2 O N 2 HN 3 N 2 H 5 + +3 +2 +1 0-1/3-2 Oxidation +5-3 Reduction Oxidation States of Chlorine HClO 4 HClO 3 ClO 2 HClO 2 HClO Cl 2 HCl +5 +4 +3 +1 0 Oxidation, AP Chem Summer Assignment Worksheet #1 Atomic Structure 1. a) For the ion 39 K +, state how many electrons, how many protons, and how many 19 neutrons are present? The enthalpy of a reaction can be estimated based on the energy input required to break bonds and the energy released when new bonds are formed. A compound that contains ions and is held together by ionic bonds is called an ionic compound. When an ionic bond forms, 1 valence electron from Na is transferred to Br to create a full octet on both atoms, now ions. (1 page) Draw the Lewis structure for each of the following. Answer the following questions. \end {align*} \nonumber \]. ~HOi-RrN 98v~c, To name an inorganic compound, we need to consider the answers to several questions. You have now created a sodium cation and a bromide anion, so you must show the charges on each outside the brackets. Element name followed by "ion" (when in Group IA, IIA, Al 3+, Ga 3+, Zn 2+, Cd 2+, Ag +, Ni 2+ ). b) Which of these particles has the smallest, Skills Worksheet Problem Solving Mole Concept Suppose you want to carry out a reaction that requires combining one atom of iron with one atom of sulfur. Hydrogen can have a maximum of two valence electrons, beryllium can have a maximum of four valence electrons, and boron can have a maximum of six valence electrons. Dont forget to show brackets and charge on your LDS for ions! Ionic bonds form instead of covalent bonds when there is a large difference in electronegativity between the ions. Compounds containing polyatomic ions are named similarly to those containing only monatomic ions, except there is no need to change to an ide ending, since the suffix is already present in the name of the anion. stream They must remain in pairs of two. Common anions are non-metals. Here, it looks like there would be 9 valence electrons but since there is a +1 charge, there should only be 8 valence electrons total. For example, the lattice energy of LiF (Z+ and Z = 1) is 1023 kJ/mol, whereas that of MgO (Z+ and Z = 2) is 3900 kJ/mol (Ro is nearly the sameabout 200 pm for both compounds). Iron typically exhibits a charge of either 2+ or 3+ (see [link]), and the two corresponding compound formulas are FeCl2 and FeCl3. If there is no prefix, then it is understood that there is only one of that element in the compound. CH 4. If the statement is false, re-write the statement to make it true. What is an ionic bond? ZnO would have the larger lattice energy because the Z values of both the cation and the anion in ZnO are greater, and the interionic distance of ZnO is smaller than that of NaCl. If the compound is ionic, does the metal form ions of only one type (fixed charge) or more than one type (variable charge)? The bond energy for a diatomic molecule, \(D_{XY}\), is defined as the standard enthalpy change for the endothermic reaction: \[XY_{(g)}X_{(g)}+Y_{(g)}\;\;\; D_{XY}=H \label{7.6.1} \]. When electrons are transferred and ions form, ionic bonds result. We saw this in the formation of NaCl. Breaking a bond always require energy to be added to the molecule. Also, all of these are predicted to be covalent compounds. Na + sodium ion, K + potassium ion, Al 3+ aluminum, Noble gases Period alogens Alkaline earth metals Alkali metals TRENDS IN TE PERIDI TABLE Usual charge +1 + +3-3 - -1 Number of Valence e - s 1 3 4 5 6 7 Electron dot diagram X X X X X X X X X 8 Group 1, Name: Class: Date: ID: A Study Guide For Chapter 7 Multiple Choice Identify the choice that best completes the statement or answers the question.