chapter 4 chemical bonding: the ionic bond...

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Chapter 4 Chemical Bonding: The Ionic Bond Model

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Ch 4.1 Chemical Bonds A chemical bond is the attractive force that holds two atoms together in a more complex unit. Ionic Bond • electron transfer between atoms • formation of ions • ionic compounds

Covalent Bond • sharing of electrons between atoms • molecules

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Properties Ionic compounds • Very ______ m.p. & b.p. • Crystalline solids, salts • Good conductors of electricity as liquids or in solution

Molecular compounds • Much ________ m.p. & b.p. • Gases, liquids, or low m.p. solids • Do Not conduct electricity

demo: compare electrical conductivity in solution

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The type of a chemical bond is determined by: • Valence shell electron configuration • Ionization energies • Electronegativities

Recall from Ch 3 that a valence electron is an electron in the outermost electron shell (valence shell) of a representative element (this includes the noble gases).

In Chem 101 - only electrons in _________ orbitals are considered valence electrons.

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Ch 4.2 Valence Electrons and Lewis Symbol This topic was covered as part of Ch 3.7. Please remember that you must depict unpaired electrons as single dots and paired electrons as pairs of dots. Please note that in your textbook, including Fig 4.1, this rule is not obeyed and that some of the symbols are considered incorrect in this course. . examples Ca : correct Ca · incorrect . . Al : correct · Al · incorrect

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Electron transfer between atoms yields electrically charged ions. Fig 4.3

Positively charged ions = cations Negatively charged ions = anions

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Ch 4.3 The Octet Rule The valence electron configurations of the noble gases are the most stable of all valence electron configurations. All noble gases except ___ have 8 valence electrons. An atom may achieve an octet by gaining, losing, or sharing valence electrons. Na 1s22s22p63s1 loses 1 valence e → Na+ 1s22s22p6 to obtain the electron configuration of Ne 1s22s22p6 Cl 1s22s22p63s23p5 adds this e → Cl- 1s22s22p63s23p6 Ar 1s22s22p63s23p6

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Ch 4.4 Ionic Bond Model & Ch. 4.5 Magnitude of Charge Metals lose valence electrons to form cations

Na+ K+ Ca2+ Mg2+ Al3+ Group IA __ IIA IIA ____ Nonmetals either share electrons or they gain valence electrons to form anions

Cl- Br- O2- S2- N3-

Group VIIA ____ VIA ____ VA The chemical properties of an ion are different than for its corresponding neutral atom. Li lithium Li+ lithium ion Ca calcium Ca2+ calcium ion

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Isoelectronic Species are an atom and ion, or two ions, that have the same electron configuration. The following ions are isoelectronic with ______

1s22s22p6 10 electrons

N3- O2- F- Na+ Mg2+ Al3+

# p 7 8 9 11 12 13 → increasing nuclear charge (Z) → decreasing atomic radii

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Supplemental Material Ionic Radii of Ions of Representative Elements Atom → Cation + e Radius ____ Atom + e → Anion Radius ____

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Ch 4.6 & 4.7 Lewis Structures and Chemical Formulas for Ionic Compounds

.. + .. - Na · + · Cl : → Na + : Cl : → NaCl . . . .

.. .. 2+ .. - Ba : + · Br : + · Br : → Ba + 2 : Br : → _______ . . . . . .

Electron Loss = Electron Gain Electrons/charges must balance to form neutral compounds

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Drill Problem: Determine the chemical formula for the ionic compound containing the ions of aluminum and sulfur

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Ch 4.8 The Structure of Ionic Compounds The electrostatic attractions between the oppositely charged ions hold ionic compounds together. Fig 4.4

The formula unit is the smallest whole-number ratio of ions present in an ionic compound with charge neutrality. Formular unit = ______

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Ch 4.9 Recognizing and Naming Binary Ionic Compounds Binary = only two elements are present Binary ionic compounds NaCl MgBr2 K3N metal + nonmetal → ionic compound cation anion Binary but NOT ionic ______ ______ covalent molecules

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NaCl sodium chloride full name of metallic element (without the term ion) + stem name and suffix of nonmetallic element name BaS barium sulfide Table 4.2 Names of selected common nonmetallic ions

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Figure 4.8 Metal ions with fixed ionic charge

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Some metal ions have variable ionic charges.

Figure 4.7 When we name compounds that contain metals with variable ionic charges, the charge on the metal ion must be specified. Copper (I) oxide Cu2O copper (I) Cu+ Copper (II) oxide CuO copper (II) Cu2+ Iron (II) chloride FeCl2 iron (II) _____ Iron (III) chloride FeCl3 iron (III) _____

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Drill problem: Name the following compound PbS2

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Ch 4.10 Polyatomic Ions

NO3- charge

# of atoms

nitrate

Table 4.3 Formulas and Names of Some Common Polyatomic Ions

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You need to know these polyatomic anions plus the corresponding ions for bromine and iodine.

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Simple steps to memorization. 1. Memorize all “ate” NO3

- ClO3- PO4

3- SO42-

nitrate chlorate phosphate sulf____ 2. One Oxygen less → “ite” suffix NO2

- ClO2-

nitrite chlor____ 3. One Oxygen more than “ate” → “per” prefix ClO4

- perchlorate 4. One Oxygen less than “ite” → “hypo” prefix ClO- hypochlorite

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5. Addition of H+ to 2- or 3- ions CO3

2- + ____ → HCO3-

carbonate bicarbonate hydrogencarbonate Note the change in the charge of the ion

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Summary for ions of sulfur S2- sulf_____ SO4

2- sulf_____ SO3

2- sulf_____ HSO4

- ___sulfate or hydrogensulfate HSO3

- ___sulfite or hydrogensulfite

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Ch 4.11 Chemical Formulas and Names for Ionic Compounds Containing Polyatomic Ions Fe(OH)3 iron (III) hydroxide NH4NO3 ammonium _______ (NH4)2CO3 ammonium carbonate

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Name the following compounds CuSO4 copper ____ sulfate KClO4 potassium perchlorate Na3PO4 sodium phosphate

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Write the chemical formula for magnesium bisulfite ____ + HSO3

- _________

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Write the chemical formula for iron (II) phosphate

____ + PO43-

__________