Do Now - March [22-5], Give three examples of things that involved nuclear chemistry. 2.What is the definition of a half-life ? 3.Draw the basic shape of a half-life graph.

Agenda Do Now/Announcements Welcome to Unit 4! Quiz-Quiz-Trade Vocabulary/Concepts Times Three! Exit Ticket

Objectives SWBAT describe ionic compounds. SWBAT determine if a bond is ionic or not using electronegativity. SWBAT draw Lewis structures for atoms.

What to expect in Unit 4 You will learn about… –Compounds (ionic and covalent) –Chemical formulas –Electronegativity, ionization energy, polarity –Naming compounds –Valence electrons continued –Lewis structures You will get to… –Quiz-Quiz-Trade! –Speed Date! –Investigate! –Show how much you know right before the GEE!

Atom - the smallest particle of an of an element

What is a compound? A compound is a pure substance A compound is a combination of two or more different elements that are chemically combined Water molecules Add to Vocabulary Log!

Familiar Compounds and Their Formulas Vinegar Acetic acid CH 2 COOH

Grain Alcohol Ethanol C 2 H 5 OH

Cane sugar Sucrose C 12 H 22 O 11

Stomach acid Hydrochloric acid HCl

What is a compound? A compound is a pure substance A compound is a combination of two or more different elements that are chemically combined Remember! Electrons do all the work in chemical bonds! Atoms do 3 things with electrons: 1.Give them away 2.Take them 3.Share them

What is a chemical bond ? A chemical bond is the force that holds two atoms together in a compound (attractive force) There are two types main types of bonds: –Ionic –Covalent Add to Vocabulary Log!

Chemical Bond Spotlight: NaCl (table salt) 2 different elements: – Sodium (Na) – Chlorine (Cl) 1 compound: – Sodium chloride (NaCl) NaCl NaCl

Chemical Bond Spotlight: NaCl (table salt)

Chemical Formula A chemical formula is a combination of chemical symbols used to represent a compound. A chemical formula contains the ratio of atoms for the compound. Add to Vocabulary Log!

Ratio Examples KBr has 1 atom of K and 1 atom of Br –This means it has a ratio of 1 K : 1 Br H 2 O has 2 atoms of H and 1 atom of O –This means it has a ratio of 2 H : 1 O CO 2 has 1 atom of C and two atoms of O –This means it has a ratio of 1 C : 2 O

Subscript Numbers Subscript numbers are placed to the lower right of element symbols and are used to show how many atoms of each element are present H2OH2OCO 2 Add to Vocabulary Log!

Chemical Formulas What is a chemical formula? What is a subscript number ? What does the subscript number tell us? If there is no number, it is an implied ONE Example: Na 2 CO 3 –2 atoms Na (sodium) –1 atom C (carbon) –3 atoms O (oxygen) –6 total atoms ( = 6) RATIO 2 Na : 1 C : 3 O

Chemical Formula Practice Determine the ratio of atoms in the following compounds. 1.N 2 2.CO 3.H 2 CO 3 4.KOH 5.CaCO 3 6.KNO 3

Ionic Bond An ionic bond is a type of bond that holds oppositely charged particles together in an ionic compound Add to Vocabulary Log!

Examples of ionic bonds Sodium chloride (NaCl) Barium chloride (BaCl 2 ) Potassium fluoride (KF) Lithium bromide (LiBr)

What to know about ionic bonds 1. Metal + Nonmetal 2.Metal gives electrons to nonmetal Metal --> Cation; Nonmetal --> Anion This deals with ionization energy STRONG bonds! High melting and boiling points Exist in crystal lattice structures Usually hard, brittle solids 1. Conduct electricity when dissolved in water 2.Have large electronegativity differences

1. Metal vs. Nonmetal Ca Cl Ca Cl

2. Ionization Energy Ionization energy is the energy required to remove one electron from an atom Trends:

3. STRONG Bonds STRONG bonds are hard to pull apart Ionic compounds want to stay together I’m so STRONG I’m ionic! Metal Nonmetal BOND!

4. Crystal Lattice Structures Crystal lattice (solid) - atoms are arranged in an orderly, geometric, 3-D structure Hard: opposite of soft Brittle: breakable (think of rock candy) Solid: describe this state of matter Na - Blue Cl - green

5. Conduct Electricity Charged particles must be free to move in order to conduct electricity In solid state, ionic compounds do not conduct electricity However, in liquid state (dissolved in water), they do conduct electricity –These are called electrolytes ! –Electric Pickle!Electric Pickle!

6. Large Electronegativity Differences Electronegativity is an atom’s ability to attract electrons to itself in a chemical bond Electronegativity is expressed in numerical values of 4.0 or less –These numerical values are called Paulings –Higher number means the atom will attract electrons in a chemical bond

Electronegativity Trends Pauling Values

How to Calculate Electronegativity Difference (DEN) 1.Look at Pauling values for each element 2.Subtract the smaller number from the bigger number Example: 4.0 (F) – 0.9 (Na) = Look at Electronegativity Rules to determine if it is ionic or not ionic Electronegativity Rules If electronegativity difference (DEN) is… 0 to 1.99: bond is not ionic 2.0 or greater: bond is ionic

DEN Practice Please work the problems in your notes.

Lewis Structures 1.Write the element symbol. 2.Determine number of valence electrons for that element. 3.Draw dots to represent valence electrons. Only pair dots up if they have to be paired! H B Cl

Lewis Structures Practice Draw Lewis structures for the following elements on the back of your notes sheet 1.K6. O 2.Be7. Br 3.Al8. Ar 4.C9. He (there’s a trick!) 5.P

Exit Ticket 1.List three characteristics of ionic bonds (things to know about ionic bonds). 2.Is the following compound ionic or not ionic? SO 2 3.Draw the Lewis structure of nitrogen. BONUS QUESTION! Why did the Electric Pickle light up?