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Understanding Ionic Compounds: Formation and Structure

Discover the formation and structure of ionic compounds through explanations of ionic bonding, electron configurations, and ion formation. Learn how to write formulas, identify ions, and predict bonding types in this comprehensive guide.

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Understanding Ionic Compounds: Formation and Structure

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  1. Chapter 3Ionic Compounds CHE 101 Sleevi

  2. Chemical Bonding valence ^ It’s all about the electrons

  3. Chemical Bonding • Atoms of elements are joined to make compounds via chemical bonds • Ionic • covalent

  4. Chemical Bonding • Elements will gain, lose or share electrons to attain the electron configuration of a noble gas • Ionic bonds • Transfer of electrons from the atoms of one element to another • Electrostatic attraction between oppositely charged ions • Covalent bonds • Sharing of electrons between adjacent atoms

  5. Ionic CompoundsIonic Bonding Ionic bonds form between: • a metal on the left side of the periodic table • a nonmetal on the right side of the periodic table Na + Cl2 NaCl sodium chloride crystals sodium metal chlorine gas

  6. Molecular CompoundsCovalent Bonding Covalent bonds are formed when two nonmetals combine, or when a metalloid bonds to a nonmetal. A molecule is a discrete group of atoms that share electrons.

  7. Chemical Bonding • Predict whether the bonds in the following species are ionic or covalent • CO • CaF2 • MgO • Cl2 • HF • C2H6

  8. Chemical Bonding • Identify the following as a compound, element or molecule • CO • CaF2 • MgO • Cl2 • HF • C2H6

  9. Ionic Compounds • neutral compound containing ions • frequently formed from a metal and a nonmetal • contain ionic bond between cation and anion • high melting point, high boiling point • most are soluble in water

  10. Formation of Ions • Ion: charged particle formed from a neutral atom by adding or removing electrons. The number of protons remains the same • Cation: positive ion, formed from metal atoms by removing one or more electrons • Anion: negative ion, formed from nonmetal atoms by adding one or more electrons • Ion formula: element symbol with the charge of the ion as a superscript (on the right)

  11. How do we determine the charge of the ion? Consider the valence electrons • Octet rule • ions are formed by the gain or loss of electrons to attain a noble gas configuration (8 e- in the valence shell)

  12. Electron Configurations and Bonding 12Mg: 1s22s22p63s2 Valence electron configuration: ___ If valence electrons are removed: 12Mg2+:1s22s22p6 10Ne: 1s22s22p6 Mg2+ is isoelectronic with Ne

  13. 3A 4A 5A 6A 8A 7A 1A 2A Periodic Table of the Elements 3B 4B 5B 6B 8B 1B 2B 7B

  14. Formation of IonsCations and Anions Cations are positively charged ions. A cationhas fewer electrons (e−) than protons.

  15. Formation of IonsCations and Anions By losing one, two, or three e−, an atom forms a cation with a completely filled outer shell of e−.

  16. Formation of IonsCations and Anions Anions are negatively charged ions. An anion has more e− than protons.

  17. A few points to remember… • Electron transfer only occurs when there is an atom to receive the electrons • Number of electrons gained or lost usually does not exceed three • Group 4A nonmetals do not usually form ions

  18. IonsRelating Group Number to Ionic Charge forGroups 1A–3A the cation charge = the group number group 1A: M 1 valence e− M+ + e− M 2 valence e− M2+ + 2e− group 2A: M 3 valence e− M3+ + 3e− group 3A:

  19. Valence Electrons and Ion Formation • Metals form cations

  20. IonsRelating Group Number to Ionic Charge forGroups 6A and 7A the anion charge = 8 – group number group 6A: X 6 valence e− + 2e− X 2− charge = 8 – 6 = 2 group 7A: X 7 valence e− + e− X − charge = 8 – 7 = 1

  21. Valence Electrons and Ion Formation • Nonmetals form anions

  22. Ion Formulas • Write ion formulas for the following elements • Lithium • Aluminum • Bromine • Calcium • Phosphorus • Oxygen

  23. IonsIons Formed by the Main Group Elements

  24. IonsMetals with Variable Charge

  25. Electron Configurations of Ions • Electrons are gained and lost such that the ion has the electron configuration of a noble gas • Ion Configurations are ISOELECTRONIC with noble gas configurations • number of protons is unchanged!

  26. Electron Configuration of Ions Write the electron configuration for the neutral atom and the ion that it forms for the following elements: a. Na b. Cl c. O d. Be

  27. Visualizing atoms and ions • Lewis Dot Structures • valence electrons are represented by dots surrounding the element symbol • put one electron on each side of symbol before pairing them

  28. Drawing Lewis Dot FormulasNeutral Atoms a. Rb b. Al c. I d. Ba e. N f. S

  29. Lewis Dot Formulas of Ions a. Ca b. P c. K d. S e. Sr f. N

  30. IonsCommon Ions in the Human Body

  31. Ionic CompoundsFormulas for Ionic Compounds The sum of the charges in an ionic compound must be zero overall.

  32. Ionic CompoundsFormulas for Ionic Compounds

  33. Illustrating the formation of ionic compounds Magnesium + Chlorine

  34. Illustrating the formation of ionic compounds Calcium + Nitrogen

  35. Ionic Compounds • Ionic compounds are neutral • the number of cations and anions needed depends on the individual charges of the ions • total positive charge + total negative charge = 0

  36. Ionic Compounds HOW TO Write a Formula for an Ionic Compound Identify which element is the cation and which is the anion. Step [1] • Metals form cations and nonmetals form anions. • Use the group number of a main group element to determine the charge. K+ K Cl− Cl Ca2+ Ca O O2− metal nonmetal nonmetal metal group 1A group 7A group 2A group 6A

  37. Ionic Compounds HOW TO Write a Formula for an Ionic Compound Determine how many of each ion type is needed for an overall charge of zero. Step [2] • When the cation and anion have the same charge, only one of each is needed. O2− + CaO Ca2+ K+ + KCl Cl− zero charge zero charge One of each ion is needed to balance charge.

  38. Ionic Compounds HOW TO Write a Formula for an Ionic Compound • When the cation and anion have different charges, use the ion charges to determine the number of ions of each needed. Ca2+ Cl− A +2 charge means 2 Cl−anions are needed. A -1 charge means 1 Ca2+ cation is needed. Cl− + CaCl2 Ca2+ 2 Cl− for each Ca2+

  39. Ionic Compounds HOW TO Write a Formula for an Ionic Compound To write the formula, place the cation first and then the anion, and omit charges. Step [3] KCl CaO CaCl2 • Use subscripts to show the number of each ion needed to have a zero overall charge. • When no subscript is written, it is assumed to be “1.”

  40. Naming Ionic CompoundsNaming Cations Main group cations are named for the element from which they are formed. Na+ K+ Ca2+ Mg2+ calcium sodium potassium magnesium

  41. Naming Ionic CompoundsNaming Cations Other cations can be named two ways: • Systematic name: Follow the name of the cation by a Roman numeral in parentheses to indicate its charge. Fe2+ Fe3+ iron(III) iron(II) • Common name: Use suffix “-ous” for the cation with a smaller charge and suffix “-ic” for the cation with a higher charge. Fe2+ Fe3+ ferrous ferric

  42. Naming Ionic Compounds

  43. Naming Ionic CompoundsNaming Anions Anions are named by replacing the ending of the element name by the suffix “-ide.”

  44. Naming Ionic CompoundsCompounds of Main Group Metals • Name the cation and then the anion. • Do not specify the charge on the cation. • Do not specify how many ions of each type are needed to balance charge. Na+ sodium F− fluoride NaF sodium fluoride + Mg2+ magnesium + MgCl2 magnesium chloride(not magnesiumdichloride) Cl− chloride

  45. Naming Ionic CompoundsCompounds of Metals with a Variable Charge HOW TO Name an Ionic Compound That Contains a Metal with Variable Charge Give the name for CuCl2. Example Determine the charge on the cation. Step [1] 2 Cl−anions = −2 total negative charge CuCl2 Cu cation must have a +2 charge to makethe overall charge zero

  46. Naming Ionic CompoundsCompounds of Metals with a Variable Charge HOW TO Name an Ionic Compound That Contains a Metal with Variable Charge Step [2] Name the cation and the anion. • cation is named one of two possible ways: Systematic Common cupric Cu2+ copper(II) • anion changes ending of element name to “-ide” Cl− chloride

  47. Naming Ionic CompoundsCompounds of Metals with a Variable Charge HOW TO Name an Ionic Compound That Contains a Metal with Variable Charge Write the name of the cation first, then the anion. Step [3] copper(II) chloride Answer = or cupric chloride

  48. Naming Ionic CompoundsWriting a Formula from the Name HOW TO Derive a Formula from the Name of an Ionic Compound Example Write the formula for tin(IV) oxide. Identify the cation and anion and determine their charges. Step [1] tin(IV)oxide tin(IV) oxide Sn4+ O O2− Sn

  49. Naming Ionic CompoundsWriting a Formula from the Name HOW TO Derive a Formula from the Name of an Ionic Compound Step [2] Balance charges. Two −2 anions are needed for each +4 cation. O2− Sn4+ Write the formula with the cation first, and use subscripts to show how many of each ion is needed to have zero overall charge. Step [3] final answer = SnO2

  50. Physical Properties of Ionic CompoundsCrystal Lattice • Ionic compounds exist in crystal lattices rather than individual molecules

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