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Warm Up 10/29. What is the difference between a mixture and a compound?. Lesson : Intro to Chemical Bonding. Chemical Bond – an attractive force between atoms that is strong enough to enable the group to act as a unit. What makes atoms bond? Why do they “want” to bond?. Dating Game.
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Warm Up 10/29 What is the difference between a mixture and a compound?
Chemical Bond – an attractive force between atoms that is strong enough to enable the group to act as a unit.
Dating Game What do you look for in a soul mate?
Like people, atoms want to feel complete. They feel complete by fulfilling the Octet Rule.
Sodium Chlorine
Octet rule – atoms tend to react and bond so that they have an outer energy level filled with electrons. • They can do this by gaining or losing electrons. • Most atoms will have 8 valence electrons after they bond. • Some will have 2 valence electrons, like hydrogen, helium, lithium, berrylium and boron.
Oxygen shares an electron pair with two hydrogen atoms, so that all of them fulfill the octet rule.
Warm Up 10/30 What electric charge does an atom have if it gains an electron? What if it loses an electron?
Lesson: Ionic Bonding Sodium chloride
Ionic Bond – electrons are transfered, then the ions attract each other. General Rules: 1) 1 Metal + 1 Non-metal 2) Elements on left lose electrons (+), elements on right gain electrons (-).
Sodium gives an electron to chlorine, so that both of them fulfill the octet rule. . +1 -1 .
Magnesium Oxide: Magnesium Oxygen -2 +2
. . -1 + 2 -1
Practice – Left side! • Directions: Write the formula units for the following ionic compounds: • Sodium & oxygen • Barium & fluorine • Rubidium & iodine • Calcium & sulfate (poly) • Potassium & sulfite (poly) • Aluminum & oxygen
Polyatomic Ions • Ions made of more than one atom (molecules that are ions) • All are anions, except ammonium • Have special names • Sulfate • Hydroxide • Phosphate
Warm Up 10/31 Give an example of a homogeneous mixture and a heterogeneous mixture.
Warm Up 11/1 If you had two liquids that formed a homogeneous mixture, what method could you use to separate them?
How to Name: • 1. Cation’s name remains unchanged • Change the end of the anion’s name to “ide” • (polyatomic ion names stay the same) • NaCl = • K O = • Al (CO ) = Sodium chloride Potassium oxide 2 Aluminum carbonate 2 3 3
Problem: Some elements have more than one form of cation! Examples: Fe and Fe We call them Iron (II) and Iron (III) Cu and Cu Call them Copper (I) and Copper (II) 2+ 3+ + 2+
Metals with Double Cations: • Ti Ti • Cr Cr • Fe Fe • Cu Cu • Au Au • SnSn • PbPb +2 +3 +2 +3 +2 +3 + +2 + +3 +2 +4 +2 +4
Use Reverse Swap & Drop! CuCl = Is it Copper (I) or Copper (II)? Fe O = Is it Iron (II) or Iron (III)? 2 2 3
What if the reverse ‘Drop and Cross’ method doesn’t work? Example: FeO
Practice: Left Side! Directions: Write the names of the following ionic compounds. • MgO • KBr • Na O • FeCl • CuBr 2 3 2
Warm Up 11/12 What is the difference between an ionic compound like salt (NaCl) and a water molecule (H 0)? 2
Old Ideas Compound = 2 atoms that are chemically bonded together. Noble gases don’t chemically react. Why? They have 8 valence electrons.
New Ideas Atoms want 8 valence electrons. That means they will have a full outer energy level. Octet rule – atoms react and bond so that they have an outer energy level filled with 8 electrons. (Some atoms only need 2)
Bonding • Covalent • Electrons shared • 2 nonmetals • Ionic • Electrons transferred • 1 metal + 1 nonmetal
What actually holds the atoms together? They are both attracted to the shared electron.
Chlorine Molecule 1 Shared pair of Electrons
Naming Covalent Compounds • Rules: • Name of the first element remains the same (might need a prefix) • Name of the second element ends in “ide” (might need a prefix) Example: S C 3
Practice Naming = Phosphorus trichloride • PCl • CO • N O • S N 3 = Carbon dioxide 2 = Dinitrogen monoxide 2 = Tetrasulfur pentanitride 4 5
Practice Writing Formulas • Selenium hexafluoride • Xenon tetrafluoride • Dichlorine heptoxide • Arsenic trifluoride • = SeF 6 • = XeF 4 • = Cl O 2 7 • = AsF 3
Left Side Practice Write the Names: 1) Br O 2) S N 3) SCl 4) Se F Write the Formulas: 5) Chlorine dioxide 6) Selenium tetrafluoride 7) Dinitrogen trioxide 8) Tetraphosphorus pentasulfide 2 4 5 4 2 3
Warm Up 11/13 What is the electron configuration of sulfur?
Warm Up 12/9 Draw the lewis dot structure for NF 3
. . . . . . . . . . . . Trigonal Pyramidal . . . . . F N F . . . . . . . . . F
Ionic Covalent • 1 Metal + 1 Nonmetal • Electrons transferred (stolen) • Swap & Drop • 2 Nonmetals • Electrons shared • Prefixes Metallic
Ionic Characteristics • Forms crystal structures • High melting and boiling points • Conducts electricity when melted • Can dissolve in water CaF 2
Covalent Characteristics • Gases, liquids or solids (molecules) • Low melting and boiling points • Poor conductors of electricity • Usually not soluble in water
Metallic Bonding The valence electrons of metals move about freely, forming a “sea” of electrons.