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Frost, Deal, and Timberlake Chapter 3 Compounds

Frost, Deal, and Timberlake Chapter 3 Compounds. Outline The Periodic Table and the electronic configurations in atoms The Octet Rule Ionic Compounds – Formulas and Nomenclature Covalent (molecular) compounds and nomenclature Covalent compounds and molecular shape

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Frost, Deal, and Timberlake Chapter 3 Compounds

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  1. Frost, Deal, and Timberlake Chapter 3 Compounds Outline The Periodic Table and the electronic configurations in atoms The Octet Rule Ionic Compounds – Formulas and Nomenclature Covalent (molecular) compounds and nomenclature Covalent compounds and molecular shape Electronegativity and bond/molecular polarity

  2. Groups or Families metal vs. nonmetal Hydrogen (H) is a nonmetal H Periods → B Si Ge As Sb Te Po At metalloids Main Group Elements (Representative Elements) – Groups 1, 2, 13-18 (excludes orange and gray blocks)

  3. Atomic # (Z) = # protons & # electrons Metal vs. nonmetal(metalloid) Period # e 1 2 2 8 3 8 4 18 5 18 6 32 7 32 Main Group elements (6 per period) electrons in p orbitals Main Group elements (2 per period) electrons in s orbitals

  4. Valence electrons – the electrons found in the outer shell (period) of the atom Groups/Families have similar valence shell electron make-up and similar chemical bonding – electrons determine chemical properties Orbitals – determine the shape of the electrons relative to the nucleus 1s2 2s2 - 2p6 3s2 - 3p6 4s2 – 3d10 – 4p6 5s2 – 4d10 – 5p6 6s2 – 4f14 – 5d10 – 6p6 7s2 – 5f14 – 6d10 – 7p6 Having a compete s-p orbital set-up is particularly stable – inert gases & octet.

  5. +1 none +2 -2 -1 -3 Ions Ion Formation +3 metals form positive ions or cations nonmetals form negative ions or anions Transition metals may have multiple + charges

  6. What ions are formed by … a) +1 b) +2 c) +3/-1 d) -2 e) -3 Barium, Ba Phosphorus, P Ions are not found isolated in nature. Naming ions ….. Cations – If it only forms 1 cation … state element name + ion e.g. Barium ion (must be +2) If it forms multiple cations … state name and charge e.g. Manganese (V) Anions – change ending of element to ‘ide’ + “ion” Group 13-16 cations in periods >2 are exceptions, like TM.

  7. Ionic Compounds On 3 name NaCl ….. Metal + nonmetal Total charge must be 0 MgCl2 is ….. a) magnesium chlorine b) magnesium chloride c) magnesium dichloride d) magnesium (II) chloride e) magnesium chloride - 2 Name: metal name + nonmetal name with “ide” ending Know but do not indicate number of ions The formula of aluminum oxide is ….. a) AlO b) AlO2 c) Al3O2 d) Al2O3 Use roman numerals to indicate charge of transition metal cations

  8. MnO is ….. a) manganese oxide b) dimanganese oxide c) manganese (II) oxide d) manganese (III) oxide The formula of Manganese (V) chloride is ….. a) Mn(V)Cl b) MnCl c) MnCl5 d) Mn(V)Cl5 Use roman numerals to indicate charge of transition metal cations

  9. Polyatomic ions are also common and form ionic compounds What is the formula for calcium carbonate? a) CaCO3 b) Ca2CO3 c) Ca(CO3)2 What is the name & formula for the compound formed by aluminum and the hydroxide ion?

  10. 3.2 In Search of an Octet, Part 1: Ion Formation too little too much Headache/fatigue hypertension Muscle weakness ← abnormal heart rhythm→ Osteoporosis heart disease rare anemia cirrhosis Acidosis alkalosis Important Ions (electrolytes) in the Body

  11. Covalent bonds are typically formed between two nonmetals Bonds between atoms in white boxes (and H)

  12. Prefixes 1 = mono (?) 2 = di 3 = tri 4 = tetra 5 = penta Binary compounds are composed of only two elements and can be named by a three-step procedure: Naming Covalent Compounds • Name the first element in the formula. • Name the second element in the formula and change the ending to -ide. • Designate the number of each element present using one of the Greek prefixes. Indicating the number of each element present is important because nonmetals can combine with each other in multiple ways. CO vs. CO2 SO2 vs. SO3 Some compounds, such as water (H2O), methane (CH4), and ammonia (NH3), are known by their traditional names.

  13. PCl5 is …. Phosphorus Chloride Phosphorus pentachloride Monophosphoruspentachloride Phosphorus (V) chloride AlCl3 is …. Aluminum Chloride Aluminum trichloride Monoaluminumtrichloride Aluminum (III) chloride N2O4 is …. Nitrogen dioxide Dinitrogen tetroxide Draw the molecular formula for nitrogen dioxide.

  14. Polyatomic ions have covalent bonding between atoms in the ion ….. hydroxide = (O – H)- or OH-. OH- forms ionic compounds with metals. Write the formula for calcium hydroxide? Name and write the formula for the Ionic compound with Cu2+ and phosphate ion? Know the polyatomic ions with →.

  15. Covalent bonding Formed when two atoms share electrons to complete octet structure. Lewis Dot Structures – representation of valence e- only useful for main group elements B 1s2 2s2 2p1 C 1s2 2s2 2p2 N 1s2 2s2 2p3 O 1s2 2s2 2p4 F 1s2 2s2 2p5 Ne 1s2 2s2 2p6 Lewis Dot Symbols for the Representative Elements & Noble Gases Note that elements in the same family have the same Lewis dot structure

  16. Lewis dot structures and covalent bond tendencies Lone pair only needs 1 e- to achieve He structure H C N O F Ne Covalent Bond A pair of electrons ‘shared’ between two atoms This is an alternate method (to ion formation) for atoms to achieve a ‘stable octet’. 4 3 2 1 0 = # electrons needed to share to form ‘octet’

  17. Covalent Bond Elements that exist as diatomic gaseous molecules include …. H2 O2 N2 F2 Cl2 etc. H● + ●H → H● ●H or H – H A covalent bond is a shared pair of electrons O O O = O

  18. Lewis Dot structures for molecules with single central atom H (or F) can’t be central atom CH4 NH3 H2O Valence electrons C = 4 H = 1 x 4 = 4 Total e = 8 Valence electrons N = 5 H = 1 x 3 = 3 Total e = 8 Valence electrons O = 6 H = 1 x 2 = 2 Total e = 8 1. Count valence electrons 4. Complete octet (2 for H) for each peripheral atom 5. Place extra electrons in pairs around central atom 6. Make sure central atom has octet – form double/triple bonds as needed 2. Draw 2D framework of molecule (geometry is not important) Put single bond between central atom and each peripheral atom

  19. The # of electrons required to complete an octet of a nonmetal is the number of covalent bonds it “typically” forms. C or Si = 4, N or P = 3, O or S = 2, H, F, Cl, …. halides = 1 Molecular formulas don’t specify bonding methane = CH4 water = H2O glucose = C6H12O6 Structural formulas are like Lewis dots without lone pairs – indicates bonding e.g. H ― O ― H May or may not indicate geometry Can we predict geometry?

  20. 3.4 In Search of an Octet, Part 2: Covalent Bonding

  21. VSEPR Valence Shell Electron Pair Repulsion • Draw the Lewis dot structure for the compound • Count the number of bonding domains around the central atom – double/triple bonds = 1 domain • Count the number of lone pairs around the central atom • Add these two numbers – this determines the electron geometry • Describe the molecular geometry based on bonding domains only Bond domains electron + lone pairsgeometry 2 3 4 linear trigonal planar tetrahedral

  22. VSEPR Valence Shell Electron Pair Repulsion All of these compounds have a tetrahedral electron geometry. Each bond angle is ~ 109º. (however : repels more then ―) CH4 NH3 H2O H | H ― C ― H | H •• H ― N ― H | H •• H ― O : | H

  23. Molecular geometry H C .. :O .. N H H H H H H H H Tetrahedral pyramid bent 3-sided All have tetrahedral electron geometries

  24. 3.6 Molecular shape Molecular Properties are influenced by shape polarity solubility physical state (solid – liquid – gas) chemical reactivity

  25. 3.7 Electronegativity and Molecular Polarity Bond Type DEN Ionic ≥ 1.8 Polar covalent 0.5 – 1.7 Nonpolar ≤ 0.4

  26. 3.7 Electronegativity and Molecular Polarity Molecular Polarity • Molecules can be polar or nonpolar. • A polar molecule has an uneven distribution of electrons over the molecule. • A nonpolar molecule has an even distribution of electrons over the entire molecule. • For molecules containing only two atoms connected by a covalent bond, the polarity of the molecule is the polarity of the bond. • When a molecule is composed of three or more atoms connected by several bonds, we must consider both the electronegativity of the atoms involved and the shape of the molecule.

  27. 3.7 Electronegativity and Molecular Polarity The bonds are polar but cancel each other. The molecule is nonpolar The polar bonds add up To make a dipole moment. The molecule is polar Each molecule has two polar bonds, but carbon dioxide is a nonpolar molecule, whereas water is a polar molecule. Carbon dioxide is a linear molecule, but water is bent.

  28. 3.5 The Mole: Counting Atoms and Compounds • The formula weight for a compound is the sum of the atomic masses. • The molar mass of a compound is numerically equal to the formula weight with units of grams/mole. Finding the Number of Molecules in a Sample • Step 1: Calculate the molar mass of the compound. • Step 2: Apply conversion factors to reach the desired unit.

  29. NA = 6.022 x 1023 atoms/molecules 1 mol Conversions # moles – FW(AW) - # atoms/molecules - mass mol g/mol # g 1 mole= the numberof C atoms in 12 g of 12C. 1 mole = 6.022 x 1023 of any item (Avogadro’s Number) A mole is like a dozen (only more) FW units = amu or g mol-1 FW (cpd) = sum of AW

  30. If I weigh out 26.7 g of Ni(NO3)2, how many moles of cpd do I have? What is my first step? Find FW of Ni(NO3)2 FW Ni(NO3)2 = 58.693 + 2 • 14.007 + 6 • 15.999 = 182.70 g/mol • 1.76 x 1023 • 0.292 • 0.146 • 5.28 x 1023 • 4878 • 6.84 • 0.146 • None of the above How many N atoms does this contain?

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