The Structure of Matter: How atoms form compounds and Chemical Bonding This information is found in Chapter 6 Sections 1 & 3. 1
Compounds Are formed when two or more elements combine (or compounds combine) There must be a chemical change There are new properties Atoms from the different elements form bonds Chemical Bond- the attractive force that holds different atoms or ions together 2
Compounds Every compound has a specific ratio of atoms Written as a chemical formula Examples: H 2 O, C 12 H 22 O 11, NaCl The ratio is the same every time! If there is a different ratio, that means there is a different compound! 3
Chemical Bonding When the valence electrons interact Atoms react to be more stable. They do this by filling their outermost energy levels Two ways to do this Share electrons Transfer electrons 4
1 2 Atoms in the same columns have the same number of valence electrons. Helium only has 2 valence electrons 3 4 5 6 7 8 5
Electron Dot diagrams (aka Lewis Structures) A way of keeping track of valence electrons. How to write them: 1) Write the symbol. 2) Put one dot for each valence electron on each of the four sides. 3) You don t pair up electrons until there is at least 5 valence electrons. X 6
The Electron Dot diagram for Nitrogen Nitrogen has 5 valence electrons. First we write the symbol. Then add 1 electron at a time to each side. N Until they are forced to pair up. 7
Na Mg C O F Ne He Write the electron dot diagram for 8
Electron Dot Notation 9
Ionic Bonding Anions (negative) and Cations (positive) are held together by opposite charges (a metal and a nonmetal element). The bond is formed through the transfer of electrons. Electrons are transferred to fill their outer level (valence electrons) 10
Charges on ions For most of the Group A elements (Representative elements), the Periodic Table can tell what kind of ion they will form from their location. Elements in the same group have similar properties. Including the charge when they are ions. 11
+1 +2 +/- 4 +3-3 -2-1 12
Electron Configurations for Cations Metals lose electrons to fill their outer level They make positive (+) ions. 13
Electron Dots For Cations Metals will have few valence electrons Ca 14
Electron Dots For Cations Metals will have few valence electrons These will come off Ca 15
Electron Dots For Cations Metals will have few valence electrons These will come off Forming positive ions Ca +2 16
Electron Configurations for Anions Non-metals gain electrons to fill their outer level They make negative (-) ions. 17
Electron Dots For Anions Nonmetals will have many valence electrons. They will gain electrons to fill outer shell. P P -3 18
Stable Arrangements All atoms react to fill their outer levels Noble gases have full outer energy levels. 8 valence electrons Also called the octet rule. Ar 19
Naming ions We will use the systematic way. Naming cations - if the charge is always the same (Representative elements) just write the name of the metal. Transition metals can have more than one type of charge. Indicate the charge with Roman numerals in parenthesis. (I, II, III, etc.) 20
Name these Na +1 Ca +2 Al +3 Fe +3 Fe +2 Li +1 Sodium ion Calcium ion Aluminum ion Iron (III) ion Iron (II) ion Lithium ion 21
Write Formulas for these Potassium ion Magnesium ion Copper (II) ion Chromium (VI) ion Barium ion Mercury (II) ion K +1 Mg +2 Cu +2 Cr +6 Ba +2 Hg +2 22
Naming Anions Anions are always named in the same way You change the element ending to ide Examples F -1 Fluorine becomes Fluoride ion Cl -1 Chlorine becomes Chloride ion Br -1 Bromine becomes Bromide ion 23
Name these ions Cl -1 N -3 Br -1 O -2 Ga +3 Chloride Nitride Bromide Oxide Gallium ion 24
Write these Sulfide ion Iodide ion Phosphide ion Strontium ion S -2 I -1 P -3 Sr +2 25
Ionic Bonding Ionic Chemical Bonding When ionic compounds form, the charges of the ions must equal zero. (the molecule has no overall charge) Ionic compounds form crystals that are held together by the charges of the ions (in specific proportions) 26
Ionic Bonding Na Cl 27
Ionic Bonding Na + Cl - 28
Ionic Bonding All the electrons must be accounted for! Ca P 29
Ionic Bonding Ca P 30
Ionic Bonding Ca +2 P 31
Ionic Bonding Ca +2 P Ca 32
Ionic Bonding Ca +2 P -3 Ca 33
Ionic Bonding Ca +2 P -3 Ca P 34
Ionic Bonding Ca +2 P -3 Ca +2 P 35
Ionic Bonding Ca Ca +2 P -3 Ca +2 P 36
Ionic Bonding Ca Ca +2 P -3 Ca +2 P 37
Ionic Bonding Ca +2 Ca +2 P -3 Ca +2 P -3 38
Ionic Bonding Ca 3 P 2 Chemical Formula 39
Ionic Compounds 1. Ionic compounds are combinations between a METAL element & a non-metal element. 2. The metal name is the same as on the periodic table. The second element ends in ide. (except for Polyatomic ions ) Examples MgBr 2 = magnesium bromide Al 2 O 3 = aluminum oxide NaCl = sodium chloride GaCl 3 = gallium chloride CaO = calcium oxide Na 2 S = sodium sulfide 40
Naming rules for Ionic compounds 1. Write the metal first and non-metal second. 2. Look up the charges of both the metal and non-metal on the periodic table (or ion chart.) 3. Add subscripts to balance the charges Use the Criss-cross 4. Write the final formula of the compound Do Not Include Charges!!! 5. Reduce subscripts to lowest common multiple (if possible) 41
Ionic Bonding: Criss-Cross Rule The Criss-cross rule (for naming ionic compounds) 1) The charge on the cation becomes the subscript on the anion (the number of anions needed). 2) The charge on the anion becomes the subscript on the cation ( the number of cations needed). 3) You do not need to write 1. (the subscripts are assumed to be 1 unless otherwise written) 42
Criss-Cross Rule Example: Aluminum Chloride Step 1: Aluminum Chloride Step 2: Al 3+ Cl 1- Step 3: Al Cl 1 3 Step 4: AlCl 3 43
Criss-Cross Rule Example: Aluminum Oxide Step 1: Aluminum Oxide Step 2: Al 3+ O 2- Step 3: Al O 2 3 Step 4: Al 2 O 3 44
Criss-Cross Rule Example: Magnesium Oxide Step 1: Magnesium Oxide Step 2: Mg 2+ O 2- Step 3: Mg O 2 2 Step 4: Mg 2 O 2 Step 5: MgO 45
Rubidium oxide Ionic Compounds Calcium phosphide Aluminum iodide Sodium fluoride Gallium sulfide Strontium selenide Cesium sulfide Barium nitride examples Rb 2 O Ca 3 P 2 AlI 3 NaF Ga 2 S 3 SrSe Cs 2 S Ba 3 N 2 46
Ionic Compounds with Transition metals Transition metals are the metallic elements in Periods 3 to 12 Remember, Metals always form POSITIVE cations In the chemical formula, these transition metals have their charges written in Roman Numerals (IN THE FORMULA) because the families/groups do not always have the same ionic charge. The Roman numerals are usually in Parentheses but not always. I = +1 II = +2 III = +3 IV = +4 V = +5 VI = +6 VII = +7 47
Ionic compounds w/transition Iron (II) oxide Iron (III) oxide Vanadium (IV) nitride Chromium (III) iodide Manganese (IV) oxide metals FeO Fe 2 O 3 V 3 N 4 CrI 3 MnO 2 48
Ionic Compounds w/ Polyatomic ions Polyatomic ions = groups of atoms that have a charge (a.k.a = radicals) Radicals can be positive or negative but most are negative. (Use your reference sheet or the back of your Periodic tables) The parentheses are used if there are multiples of the groups when writing the formulas Examples: Ammonium = (NH 4 ) +1 Hydroxide = (OH) -1 Borate = (BO 3 ) -2 49
Ionic Compounds w/ Polyatomic ions Sodium nitrite Sodium nitrate Potassium oxalate Transition metals w/ Polyatomic Ions Iron (II) nitrate Vanadium (IV) sulfate Na(NO 2 ) Na(NO 3 ) K 2 (C 2 O 4 ) Fe(NO 3 ) 2 V(SO 4 ) 2 50
Properties of Ionic Compounds They have Crystalline structure. They have regular repeating arrangement of ions in the solid. Ions are strongly bonded (many small bonds add up to a really strong bond) Structure is rigid! High melting points- because of strong forces between ions. 51
Crystalline structure Crystals for when different ions w/ different charges (+ or -) are held together by their opposite charges There are many different crystal arrangements 52
Gout is a condition related to uric acid crystals 53
Ionic solids are brittle + - + - - + - + + - + - - + - + 54
Ionic solids are brittle Ionic compound break apart in solid phase. - + - + + - + - - + - + 55
Ionic compounds, Do they Conduct? Conducting electricity is allowing charges to move. In a solid, the ions are locked in place, therefore Ionic solids are insulators (non-conductors) When melted, the ions can move around. Melted ionic compounds conduct. At very high temps. ~800ºC. Dissolved in water (solutions) Ionic compounds are good conductors!!! 56