Covalent (Molecular) compounds and. Chapter 7 & 8. Bonding

Transcription

1 Covalent (Molecular) compounds and Chapter 7 & 8 Bonding

2 Where are covalent compounds found? Water Sugar Cooking Oil Protein Candle wax Chocolate Lipstick Plastics Paper Cotton Fingernail polish Hair Food Mothballs

3 Bonding Bonds can form when atoms share electrons, called a covalent bond. Occurs between 2 or more nonmetals. A molecule is formed when we have a covalent bond. Formula unit is used for ionic compounds.

4 Molecular Compounds These are composed of two or more non-metals and form molecules covalently bonded (they share valence electrons). Because of the weak forces, molecules have low melting and boiling points. Can t use charges to figure out how many of each atom Many are flammable not very soluble in water Variety of colors of compounds Nonconductors of electricity and heat Are not electrolytes

5 Smallest piece is called a molecule Valence electrons are shared by atoms not transferred so NO ions. Typically are gases and liquids at room temperature If a solid, soft and brittle (amorphous solids) If in a network then hard and brittle (diamond & graphite) Few are crystalline (diamond & sugar)

6 Characteristics Covalent compounds are held together by weak forces called intermolecular forces or van der Waals forces 1. Nonpolar molecules: dispersion forces (weakest) 2. Polar molecules: dipole-dipole force (middle) 3. Hydrogen bonds: occur between H and another highly electronegative atom (strongest)

7 How to tell the type of bond Find the electronegativity difference on the back of the PT. Pure covalent [(0.4) polar cov [(1.7) ionic (non-polar) Lowercase delta (δ) means partially So δ- means the atom has a slight negative charge but not enough to be an ion

8 Bond Polarity a) Metallic: delocalized valence e-, (sea of electrons), piece of metal, good electrical conductors, very strong bond, very high mp/bp. Ex. Gold ring, copper wire, steel basket, etc. b) Ionic: usually metals with non-metals, absolute Electronegativity difference greater than 1.7, brittle, high mp/bp, strong bond, hydrophillic. So e- have been transferred from Ca to Cl, will form 3 separate ions in solution, Ca 2+ Cl 1- Cl 1-

9 c) Pure covalent bond: generally nonmetals, electrons shared equally between the 2 atoms, weak bonds, low mp/bp, hydrophobic, lipophilic Electronegativity difference < 0.4 Ex. Methane (CH 4 ) = 0.35 d) Polar covalent bond: generally nonmetals, electrons shared unequally between the 2 atoms, weak bonds, low mp/bp, hydrophilic, lipophobic

10 Examples Ex. Ca Cl = 2.16 Hint: look at each bond individually (don t multiply by 2) So bond is ionic Ex. Water H 2 O = 1.27 So bond is polar covalent For polar compounds draw the delta and delta + Ex δ- O H δ+ The element with the highest electronegativity gets the δ-.

11 Naming Molecular Ionic compounds use charges to determine how many of each. Have to figure out charges. Have to figure out numbers of atoms. Molecular compound name tells you the formula. Uses Greek prefixes to tell you the number of atoms, NOT Roman numerals

12 Prefixes (See Ion Sheet) 1 = mono- 2 = di- 3 = tri- 4 = tetra- 5 = penta- 7 = hepta- 8 = octa- 9 = nona- 6 = hexa- 10 = deca- Exception is: we only write mono- if there is no other prefix used.

13 Name These N 2 O NO 2 Cl 2 O 7 CBr 4 CO 2 Water? Ammonia? Methane? BaCl 2

14 Write formulas for these 1. diphosphorus pentoxide 2. tetraiodine nonoxide 3. sulfur hexafluoride 4. nitrogen trioxide 5. carbon tetrahydride 6. phosphorus heptafluoride 7. xenon octachloride

15 Name these molecular compounds (for a grade) 1. NO 2 9) H 2 O 2 2. N 2 O 10) N 5 O CO 11) CCl 4 4. C 2 H 6 O 7 12) CH 3 O 4 5. H P O 4 6. H Se 6 Cl 7. C 7 H 8 N 9 8. H 8 Br 6

16 Name these molecular compounds (for a grade) 1. NO 2 2. N 2 O 3. CO 4. C 2 H 6 O 7 5. H P O 4 6. H Se 6 Cl 7. C 7 H 8 N 9 8. H 8 Br 6 9. H 2 O N 5 O CCl 4 1. nitrogen dioxide 2. dinitrogen oxide 3. carbon monoxide 4. dicarbon hexahydrogen heptoxide 5. hydrogen phosphorous tetroxide 6. hydrogen hexaselenium chloride 7. heptacarbon octahydrogen nonanitride 8. octahydrogen hexabromide 9. dihydrogen dioxide 10.pentanitrogen decoxide 11.carbon tetrachloride 12.carbon trihydrogen tetraoxide 12. CH 3 O 4

17 Bellringer 1. Name H 2 O 2 2. Write the formula for nitrogen monoxide 3. Ionic compounds are made of a and a in general. 4. Covalent compounds are made of a and a in general. 5. Of the 2 types, have higher melting points.

18 Quiz warm-up Use the Ion Sheet for electronegativities. 1. List the 3 types of intermolecular forces. 2. What type of IF do polar compounds have? 3. What is a dipole? 4. Determine the type of bond in P-I 5. Draw the bond and indicate any partial charges in C-F 6. Name C 2 H 6 O 7 7. What is a network solid, is it ionic or covalent and give an example.

19 GEN Quiz warm-up Use the Ion Sheet for electronegativities. 1. The 4 types of bonds are,. and. 2. Bonds that have a total separation of charges are called. 3. Bonds with partial charges are called. 4. A partial charge is indicated with the Greek letter. 5. Determine the type of bond in P-I 6. Draw the bond and indicate any partial charges in C-F 7. Name C 2 H 6 O 7 8. Name SH 3 N 4

20 Videos Convert diamond to graphite Tyler Ionic vs Cov Covalent bonding Ionic covalent or polar? Hydrogen bonds Properties of compounds Amorphous vs Crystalline Diamonds from peanut butter

21 Acids Characteristics, Writing names and Formulas

22 Acids These compounds produce hydrogen ions (H+) when dissolved in water (also written as H 3 O 1+, hydronium ion ).

23 Acids There will usually be an H next to an anion. Sour tasting, turn litmus red, corrosive There are 3 main definitions of acids which will be covered in another chapter.

24 Naming Binary acids If the anion attached to hydrogen ends in -ide, put the prefix hydro- and change ide to -ic acid HCl... hydrogen ion and chloride ion = hydrochloric acid H 2 S..hydrogen ion and sulfide ion = hydrosulfuric acid

25 Ternary acids (H and 2 elements) per -ic (has most oxygen) if anion is ate, change to ic if anion is ite, change to ous hypo -ous (has least oxygen) Ex. SO 4 2- is sulfate so H 2 SO 4 is Ex. SO 3 2- is sulfite so H 2 SO 3 is Sulfuric acid Sulfurous acid HNO 3 = anion is nitrate, the suffix -ate changes to -ic so is Nitric acid HNO 2 = anion is nitrite, the suffix -ite changes to -ous.so is Nitrous acid

26 Try these! Name as ACIDS HCl HNO 3 HNO 2 H 3 PO 4 H 2 CO 3 Hydrochloric acid Nitric acid Nitrous acid Phosphoric acid Carbonic acid

27 Writing Acid Formulas Hydrogen will always be first name will tell you the anion make the charges cancel out. Starts with hydro?- no oxygen, -ide no hydro?, -ate comes from - ic, -ite comes from -ous

28 Assignment Acid Practice 1 Name these as covalent AND as acids 1. HF 10. HClO 2. H 3 P 11. HClO 2 3. H 2 SO HClO 3 4. H 2 SO HClO 4 5. HCN 14. H 3 PO 3 6. H 2 CrO H 3 PO 4 7. Hydroiodic acid 16. Acetic acid 8. Carbonic acid 17. Phosphorous acid 9. Hydrobromic acid 18. Bromic acid

29 Name these 1st 1. HF 7. HClO 2. H 3 P 8. HClO 2 3. H 2 SO 4 9. HClO 3 4. H 2 SO HClO 4 5. HCN 6. H 2 CrO 4

30 Write formulas for these hydroiodic acid acetic acid carbonic acid phosphorous acid hydrobromic acid

31 Helpful to remember In an ionic compound, the net ionic charge is zero (criss-cross method) 2. An -ide ending generally indicates a binary compound 3. An -ite or -ate ending means there is a polyatomic ion that has oxygen 4. Prefixes generally mean molecular; they show the number of each atom 5. A Roman numeral after the name of a cation shows the ionic charge of the cation

32 Practice 1 Calcium oxide 6 Na 3 P 2 Cobalt (III) oxide 7 Fe 3 P 2 3 Diphosphorous tetroxide 8 N 2 O 7 4 Sulfuric acid 9 H 2 SO 3 5 Hydrosulfuric acid 10 H 3 P

33 Hints for Naming Acids Hydrogen is the first element in an acid Rules 1. If made of only 2 types of elements, the name starts with hydro- 1. The 2 nd element is named and the ending is ic 2. Add the word acid to the end 2. If a polyatomic, 1. if the name of the polyatomic ends in ate, replace with ic 2. if it ends with ite, replace with ous 3. Add acid to the end

34 Examples HI = Hydrosulfuric acid = Sulfurous acid = Sulfuric acid = H 3 PO 4 =

35 Name as acids: 1) HF 2) H 2 CO 3 3) H 2 S Lab today, Quiz Friday over acids 4) H 3 PO 3 5) HC 2 H 3 O 2

36 Write the formula 6) Sulfurous acid 7) Oxalic acid 8) Phosphorous acid 9) Hydrotelluric acid 10)Boric acid

37 Bellringer 1. The ph scale goes from to. 2. Acids are on the ph scale. 3. Write the formula for Hydrotelluric acid. 4. Write the formula for Boric acid. 5. Name H IO 3 as an acid.

38 Hydrates Compounds (covalent or ionic) with water trapped in the crystal (and formula) Do not look wet A colorful example is cobalt(ii) chloride, which turns from blue to red upon hydration (used as a water indicator). Anhydrous = no water in the crystal Anhydrous cobalt(ii) chloride CoCl 2 Hydrated Cobalt(II) chloride hexahydrate CoCl 2 6H 2 O

39 Name as an ionic compound, then add a Greek prefix to indicate the number of water molecules. Ex. Name Cu SO 4. 5 H 2 O Copper (II) sulfate pentahydrate Ex. Name: Zn PO 4. 3 H 2 O Zinc phosphate trihydrate

40 Naming Hydrates 1) Cu (NO 3 ) 2 3 H 2 O 2) Al (OH) 3 6 H 2 O 3) Cu NO 3 9 H 2 O 4) Fe (NO 2 ) 2 H 2 O 5) Zn (CN) 2 6 H 2 O

41 e/hydrate.html Chem team hydrates

42 Tutorials Formulas compounds: o&view=detail&mid=3888cfdf f233888cfdf F23&first=0&qpvt=ionic+bond+video Naming compounds: o&view=detail&mid=3888cfdf f233888cfdf F23&first=0&qpvt=ionic+bond+video Junior chem formulas s&view=detail&mid=3df42fcae87f9787c4413df42fcae8 7F9787C441&first=41