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Chemical Bonds

Chemical Bonds. staff.tuhsd.k12.az.us/ldompier/ChmPhyPP%5CCh.%206.ppt. TEKS. 7 (A) name ionic compounds containing main group or transition metals, covalent compounds, acids, and bases, using International Union of Pure and Applied Chemistry (IUPAC) nomenclature rules;

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Chemical Bonds

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  1. Chemical Bonds staff.tuhsd.k12.az.us/ldompier/ChmPhyPP%5CCh.%206.ppt

  2. TEKS 7 (A) name ionic compounds containing main group or transition metals, covalent compounds, acids, and bases, using International Union of Pure and Applied Chemistry (IUPAC) nomenclature rules; 7 (B) write the chemical formulas of common polyatomic ions, ionic compounds containing main group or transition metals, covalent compounds, acids, and bases; 7 (C) construct electron dot formulas to illustrate ionic and covalent bonds; 7 (D) describe the nature of metallic bonding and apply the theory to explain metallic properties such as thermal and electrical conductivity, malleability, and ductility;

  3. Objectives • Explain why atoms form bonds • Define chemical bond & name three types of chemical bonds • Compare and contrast the advantages and disadvantages of varying molecular models

  4. Bonding Atoms • Why do atoms bond? - each atom wants a full outermost energy level - gain, lose, and share valence electrons to achieve the duet or octet rule aka: “being happy” - gives each atom an electron configuration similar to that of a noblegas ex. Group 18: He, Ne, Ar

  5. Chemical Bonds • Chemical Bonds - attractive force that holds atoms or ions together - 3 types ionic, covalent, metallic - determines the structure of compound - structure affects properties - melting/boiling pts, conductivity etc.

  6. Chemical Structure/Models • Chemical Structure/Molecular Models - arrangement of bonded atoms or ions - bond length: the averagedistance between the nuclei of two bonded atoms - bond angles: the angle formed by two bonds to the sameatom

  7. Molecular Models of Compounds • Ball and stick - atoms are represented by balls - bonds are represented by sticks * good for “seeing” angles • Structural - chemical symbols represents atoms - lines are used to represent bonds * good for “seeing” angles H H O

  8. Molecular Models Cont. • Space filling - colored circles represent atoms, and the space they take up - no bonds, no bond angles • Electron Dot/Lewis Structure - chemicalsymbol represent atom - dots represent valenceelectrons - 2 center dots represent a bond - no bond angles, no bond length

  9. Objectives • Describe how an ionic, covalent and metallic bonds forms • Relate the properties of ionic compounds to the structure of crystal lattices • Compare polar and non polar bonds, and demonstrate how polar bonds affect polarity of a molecule • Describe the structure and strength of bonds in metals & relate their properties to their structure

  10. Ionic Bonds / Ionic Compounds • Definition - bond formed by the attraction between oppositely charged ions cation: positive: lost e-’s anion: negative: gained e-’s - oppositely charged ions attract each other and form an ionic bond ex. Na+ + Cl- = NaCl - electrons are transferred from one atom to another - negative ions attract more positive ions, and soon a network is formed

  11. Ionic Bonds Cont.

  12. Networks / Crystal Lattices • Networks - repeating pattern of multiple ions ex. NaCl - every Na ion is next to 6 Cl ions - strong attraction between ions creates a rigid framework, or lattice structure: aka: crystals ex, cubes, hexagons, tetragons

  13. Properties of Ionic Compounds • Structure affects properties - strong attractions between ions: strong bonds - high melting/boiling pt - shatter when struck (think of it as one unit) - conductivity solid: ions are so close together, fixed positions, (can’t move) NO conductivity liquid: ions are freely moving due to a broken lattice structure Good conductivity

  14. Covalent Bonds • Definition - chemical bond in which two atoms share a pair of valenceelectrons - can be a single, double, or triple bond single, 2e-’s (-); double, 4e-’s (=); triple, 6e-’s( ) - always formed between nonmetals - mostly low melting/boiling points • 2 types of bonds - polar - non polar

  15. Covalent Bond Cont. • Non Polar - bonded atoms that share e-’s equally - same atoms bonded ex. Cl – Cl: Cl2 • Polar - bonded atoms that do not share e-’s equally - different atoms bonded H ex. H – N – H: NH3

  16. Covalent Bonds Cont.

  17. Metallic Bonds • Definition - a bond formed by the attraction between positively charged metalion (cation) and the sharedelectrons that surround it (sea of electrons) ex. Cu • Properties - Conductivity: Good: electrons can move freely - Malleable: lattice structure is flexible

  18. Metallic Bonds Cont.

  19. Predicting Bond Type

  20. Objectives • Recognize monoatomic ions, metals with multiple ions and polyatomic ions • Name and determine chemical formulas for monoatomic ions, metals with multiple ion and polyatomic ions

  21. Naming Ions • Monoatomic Ions - cation -name of element with ion ex. (Na) Sodium (Na+) Sodium ion - anion - name of element with the suffix –ide ex. (Br) Bromine (Br-) Bromide • Ions with multiple cations - transition metals - most form 2+, 3+ and 4+ ex. Cu+, Cu2+

  22. Naming Metals with Multiple Ions • Transition Metals - form multiple ions - in order to name the ion use a romannumeral to indicate the charge ex. Cu2+: Copper (II), Titanium (III): Ti3+ Practice Problems: Fe3+: Iron (III) Mercury (III): Hg3+ Pb4+: Lead (IV) Chromium (II): Cr2+

  23. Polyatomic Ions • Definition - an ion made of one or more atoms that are covalently bonded and that act as a unit (atoms that have lost or gained electrons) ex. CO3 2- , NH4+ - behave the same as other ions - polyatomic ions can combined like any other ion (as a unit) ex. NH4NO3 1:1 ratio (NH4)2SO4 2:1 ratio

  24. Polyatomic Ions • Naming polyatomic ions - not logical - rules for some compounds • -ite & -ate endings - indicates the presence of oxygen - called oxyanions - if (-) does not specify how many oxygen atoms are present ex. Sulfate:4, Nitrate:3, Acetate:2

  25. Polyatomic Ions Cont. - often several oxyanions differ only in the number of oxygen atoms present ex. Sulfur - ion with more oxygen takes the –ate ending ex. SO4 - ion with less takes the –ite ending ex. SO3 • Common Oxyanions * Make sure you know these: memorize

  26. Polyatomic Ions Cont. • Common Polyatomic Ions

  27. Objectives • Name ionic compounds from formulas • Determine the chemical formulas for ionic compounds from compound name

  28. Naming Ionic Compounds • Naming ionic compounds (binary) Formula to Name - name of cation followed by the name of the anion ex. NaCl: Sodium Chloride ZnO: Zinc (II) Oxide CuCl2: Copper (II) Chloride - formulas must indicate the relative number of cations and ions if transitional

  29. Naming Ionic Compounds • Practice Problems MgBr2 Magnesium Bromide KI Potassium Iodide CuCl2 Copper (II) Chloride Fe2S3 Iron (III) Sulfide

  30. Formulas of Ionic Compounds • Writing formulas for ionic compounds Name to Formula - balance the cation charge and anion charge, leaving NO netcharge - use subscripts to denote the number of atoms in the formula ex. NaCl: Na+ Cl- : NaCl CaCl: Ca2+ Cl- : CaCl2 **1 to 1 ratios do not designate charge** **Criss-Cross charges into subscripts**

  31. Practice Problems • Write the formula for the following atoms a. lithium oxide Li2O b. beryllium chloride BeCl2 c. titanium (III) nitride TiN d. cobalt (III) hydroxide Co(OH)3

  32. Objectives • Name Covalent compounds from formulas • Determine the chemical formulas for covalent compounds from compound name

  33. Naming Covalent Compounds • Prefix System # of atoms prefix 1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca

  34. Naming Covalent Compounds Cont. • Rules for the prefix system 1. less electronegative element is given first. It is given a prefix only if it contributes more than one atom to a molecule of the compound 2. The second element is named by combining (a) a prefix indicating the number of atoms contributed by the atom (b) the root of the name of the second element, and (c) the ending –ide 3. The o or a at the end of a prefix is usually dropped when the word following the prefix begins with another vowel ex. Monoxide or pentoxide

  35. Naming Covalent Compounds Cont. Naming covalent compounds from formula 1. SiO2 Silicon dioxide 2. PBr3 Phosphorus tribromide 3. CI4 Carbon tetraiodide 4. N2O3 Dinitrogen trioxide

  36. Writing Formulas for Covalent Compunds • Writing formulas from names • Carbon Dioxide CO2 • Dinitrogen Pentoxide N2O5 3. Triphosphorus monosulfide P3S 4. Sulfur Monobromide SBr

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