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Chapter 6 Chemical Bonds.

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Presentation on theme: "Chapter 6 Chemical Bonds."— Presentation transcript:

1 Chapter 6 Chemical Bonds

2 6.1 Ionic Bonding Stable electron configuration – when the highest occupied energy level of an atom is filled with electrons, it is stable and not likely to react Ex. = Noble Gases (He = 2 v.e., others = 8 v.e.) “8 is great” Nature always strives for stability (8 v.e.) Need to be able to see the electron configuration

3 Electron Dot Diagram Li Be B C N
A model to show the valence electrons for any element Developed by G.N. Lewis in 1916 Only shows Symbol & valence electrons Ex. H He Li Be B C N

4 O F Ne

5 Ionic Bonds Elements that have unfilled outer energy levels (incomplete sets of v.e.) tend to react with other elements Some elements achieve a stable electron configuration through transfer of electrons between atoms Ex. Na Cl → Na+ Cl -

6 Formation of Ions When an atom gains or loses an electron, the # of protons & electrons is no longer = The charge on the atom is not balanced and the atom is not neutral An atom that has a + or – electric charge is called an ion We show this by placing a plus or minus sign by the symbol

7 Ions Anion = is an ion which has gained an electron (Cl- in the last slide) “a negative ion” = anion (anion = has one extra electron) Name it by the root & -ide (ex. Chloride) Cation = is an ion which has lost an electron (Na+ in the last slide) (cation = has one fewer electron) Name it by element only (ex. Sodium ion)

8 Bonds Chemical Bond = force that holds atoms or ions together as a unit Ionic bond = force that holds cations & anions together when electrons are transferred from one atom to another Covalent bond = chemical bond where 2 atoms share a pair of electrons

9 Ionization Energy It takes more energy to remove an electron from Fluorine than from a metal in Group 1 Easiest to remove from the bottom of Group 1 Ionization energy generally increases as you move up the P.T. Generally Increases & toward nonmetals Generally Increases

10 Ionic Compounds Compounds with Ionic bonds are Ionic Compounds
Chemical Formulas show the ratio of the atoms or ions of elements in the compound (subscript # tells how many) If there is only 1, subscript is not needed NaCl = 1 Na (Sodium ion) & 1 Cl (Chloride ion) ? How many of each in MgCl2, CO2, Al2S3

11 Crystal Lattices Chemical formula tells you the ratio of ions in a compound but not how they are arranged Solid particles in a lattice structure are called crystals (they have flat sides naturally)

12 Properties of Ionic Compounds
High melting point (ex: NaCl = 801°C) In solid state = poor conductor, but in melted state = good conductor of electricity Crystals shatter when struck by a hammer Properties of an ionic compound can be explained by the strong attractions among ions within a crystalline lattice

13 Cave of Crystals – in Mexico

14 6.2 Covalent Bonding Covalent Bonding
= sharing electrons (“cooperating”) Nonmetals form covalent bonds Ex. = H2 Electron Dot Diagram Structural Formula H H H H Diatomic molecules (2 atoms) –gens & -ines Molecule = neutral group of atoms joined by 1 or more covalent bonds

15 Multiple Covalent Bonds
More than 1 pair of electrons can be shared Represented by a long dash between the element symbols Ex. N N shows a triple bond between Nitrogen atoms Ex. H H shows single & double bonds C C H H

16 Unequal Sharing of Electrons
In general elements on the right side of the P.T. have a greater attraction for electrons than elements on the left (except Noble Gases) Element w/ strongest attraction = Fluorine

17 Polar Covalent Bonds A covalent bond where the electrons are not shared equally is called a polar covalent bond The atom with the greater attraction for electrons has a partial negative charge & the other atom has a partial positive charge Type of atoms & shape (arrangement) determine if the molecule is polar or nonpolar Attraction is stronger b/t polar molecules

18 6.3 Naming Compounds & Formulas
Binary Ionic Compounds – easiest b/c we use the name of the cation & then the anion with –ide on the end of the root name NaCl = Sodium Chlor ide = Sodium Chloride CaO = ? Calcium + Ox + ide = ? Calcium Oxide

19 Common Anions (P. 171 chart)
F = Fluorine = Fluor + ide Cl = Chlorine = Chlor + ide Br = Bromine = Brom + ide I = Iodine = Iod + ide O = Oxygen = Ox + ide S = Sulfur = Sulf + ide N = Nitrogen = Nitr + ide P = Phosphorus = Phosph + ide

20 Some Metal Cations (p. 172) Copper(I) = Cu+ Copper(II) = Cu+2
Iron(II) = Fe+2 Iron(III) = Fe+3 Lead(II) = Pb+2 Lead(IV) = Pb+4 Notice the Roman Numerals in parentheses Chromium(II) = Cr+2 Chromium(III) = Cr+3 Titanium(II) = Ti+2 Titanium(III) = Ti+3 Titanium(IV) = Ti+4 Mercury(II) = Hg+2 = tells you what the oxidation # is for that isotope of the element

21 Some Polyatomic Ions (p. 173)
Ammonium NH4+ Hydroxide OH- Nitrate NO3- Sulfate SO4-2 Carbonate CO3-2 Phosphate PO4-3 Chromate CrO4-2 Silicate SiO3-2 Acetate C2H3O2- Peroxide O2-2 Permanganate MnO4- Hydrogen Sulfate HSO4- Hydrogen Carbonate HCO3- Hydrogen Phosphate HPO4-2 Dichromate Cr2O7-2 Hypochlorite OCl-

22 Prefixes for Naming Compounds
1 = mono 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa 7 = hepta 8 = octa 9 = nona 10 = deca If a formula gives you prefixes, use those numbers regardless of balancing

23 Writing the Formula If you know the name, you can write the formula
1st write symbol for the cation 2nd write symbol for the anion 3rd add subscripts to show the ratio of the ions in the compound (total charges must = 0 “neutral”) H+1 O-2 looks like H2O for it to be balanced or neutral It takes 2 H+1 to balance or neutralize 1 O-2

24 Write the Formula Calcium Oxide Copper (I) Sulfide Sodium Sulfate
Sodium Hydroxide Lithium Oxide Iron (III) Oxide Nitrogen Dioxide Dinitrogen Tetraoxide Sodium Pentoxide Diphosphorus Tetrafluoride

25 Write the Formula Calcium Oxide Copper (I) Sulfide Sodium Sulfate
Sodium Hydroxide Lithium Oxide Iron (III) Oxide Nitrogen Dioxide Dinitrogen Tetraoxide Sodium Pentoxide Diphosphorus Tetrafluoride CaO Cu2S Na2SO4 NaOH Li2O Fe2O3 NO2 N2O4 NaO5 P2F4

26 6.4 Metallic Bonds Metallic bond = the attraction b/t a metal cation & the shared electrons that surround it In a metal = valence electrons are free to move around the atoms This is why metals are malleable & ductile Metals w/ less v.e. are not as strong as those with more v.e. (ex. Sodium can be cut with a butter knife, but Tungsten is harder and has a higher melting pt.)

27 Alloys Alloys = mixture of 2 or more elements where at least 1 is a metal & they have the characteristic properties of a metal Gold = 24kt = 100% pure (soft, bends) 18kt = 75% 14kt = 58% 12kt = 50% (stronger)

28 Other Alloys Bronze = alloy of copper & tin
both are soft metals but are harder and stronger when put together in an alloy Used for propellers on ships and statues Brass = alloy of copper & zinc brass is softer & can be shaped easier Used for instruments (French Horn, bells)

29 Other Alloys (cont’d) Steel = alloy of Iron & small amt of Carbon
Carbon bonds with Iron and makes it stronger than iron alone Stainless Steel has Chromium and very little Carbon in the alloy with Iron Steel wires used as bridge cables have S, Mn, P, Si, and C mixed with Fe to allow the cables to resist breaking when they are pulled.

30 Steel wires used as bridge cables have S, Mn, P, Si, and C mixed with Fe to allow the cables to resist breaking when they are pulled.

31 Study for your TEST Friday, March 21, on Ch. 6
Ch. 7 when we come back from Spring Break We will have vocabulary quiz for Ch. 7 on Thursday, April 3

32 TEST Friday, 3/21 Know your chemical names and formulas
This sign appeared at Louisville Waterfront Park It was posted on the large water fountain in the park

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