The Structure of matter Physical Science - Chapter 5 Jones

What will we be learning? Section 1: Compounds and Molecules Distinguish between compounds and mixtures (review from Ch 2!). Relate the chemical formula of a compound to the relative numbers of atoms or ions present in the compound (ALSO review from Ch 2!). Describe how the chemical structure of a compound affects its properties.

“Compound” What does this word mean? Something that involves more than one thing Examples: Compound fracture Compound sentence Chemical compound

Examples of Chemical Compounds H2O C6H12O6 CO2 Pop Quiz! Are CO and CO2 the same compound? CO = carbon monoxide, and CO2 = carbon dioxide

Examples of Chemical Compounds H2O C6H12O6 CO2 Pop Quiz! Are CO and CO2 the same compound? CO = carbon monoxide, and CO2 = carbon dioxide NO! They have different numbers of oxygen atoms. This makes them different compounds.

How are these atoms put together? Chemical bonds – the attractive forces that hold different atoms or ions together Chemical bonds can form between atoms and can also be broken Na + Cl  Na-Cl (written as NaCl, bond formed) NaCl  Na + Cl (bond broken)

Chemical formulas Chemical formulas represent the numbers and types of atoms in a compound A compound will always have the same chemical formula Example: H2O will always be water NaCl will always be sodium chloride

Chemical Structure The structure will differ between compounds based on the types of bonds between atoms. Strong solids have network structures All molecules in the structure are the same shape, including the angles of the atoms. This arrangement holds the atoms together in a strong rigid structure.

Chemical Structure The structure will differ between compounds based on the types of bonds between atoms. Some compounds are networks made of bonded ions (ionic compounds) Sodium chloride – Na+1 and Cl-1 ions are attracted to each other and form crystal-shaped structures VERY strong bonds

Chemical Structure The structure will differ between compounds based on the types of bonds between atoms. Some compounds made of molecules (molecular compounds, also called covalent bonds) Glucose - C6H12O6, not ions, but whole molecules attracted to each other to form crystals Weaker bonds

How does bond strength affect a compound’s properties? Network Structures Ionic Compounds Molecular Compounds/Covalent Bonds VERY STRONG BONDS High melting points (in the thousands) High boiling points (in the thousands) Strong bonds High melting points (high hundreds to low thousands) High boiling points (high hundreds to low thousands) Weaker bonds Lower melting and boiling points (usually less than 100) Therefore, we can conclude that the stronger the bond, the more energy (high melting and boiling points) it takes to break the bonds. The weaker the bond, the less energy it takes to break the bonds.

Hydrogen Bonds Another force of attraction in compounds Forms between adjacent hydrogen atoms of molecules Strong bonds Gives water special characteristics Surface tension – the force between water molecules that gives it a droplet shape

Ch 5 Sec 1 Quiz Choose the term that best completes each sentence. The atoms in a compound are held together by (chemical bonds/chemical structure). A compound’s (chemical formula/bond angle) shows which atoms or ions it is made up of. Network solids usually have (high/low) melting and boiling points.

Ch 5 Sec 1 Quiz Choose the term that best completes each sentence. The atoms in a compound are held together by (chemical bonds/chemical structure). A compound’s (chemical formula/bond angle) shows which atoms or ions it is made up of. Network solids usually have (high/low) melting and boiling points.

What will we be learning? Section 2: Ionic and Covalent Bonding Explain why atoms sometimes join to form bonds. Explain why some atoms transfer their valence electrons to form ionic bonds, while other atoms share valence electrons to form covalent bonds. Differentiate between ionic, covalent, and metallic bonds. Compare the properties of substances with different types of bonds.

Why do atoms bond together? Valence electrons - which atoms have a full set of 8 electrons and do not need to lose or gain electrons?

Why do atoms bond together? Valence electrons - which atoms have a full set of 8 electrons and do not need to lose or gain electrons? Noble gases – they are stable **Atoms form bonds to become stable** The type of element and how many valence electrons it has determines what it can bond with.

Ionic Bonds Formed between oppositely charged ions Example: Na+1 + Cl-1  NaCl Characteristics of ionic bonds & compounds Electrons are transferred (the chlorine atom GAINED the electron that the sodium atom LOST). Usually between a metal and a nonmetal Stronger than covalent bonds High melting points and boiling points Conduct electricity when dissolved in water Can include polyatomic ions

Ionic Bonds Polyatomic ions – a charged molecule that contains one or more types of atoms Always put parentheses around a polyatomic ion and write the charge on the outside The charge will never change The types of atoms and subscripts will never change Examples: P 158 Table 3

Formulas of Ionic Compounds In order to write the formula for a compound, the charges must be determined. Magnesium fluoride Mg+2 + F-1 

Formulas of Ionic Compounds In order to write the formula for a compound, the charges must be determined. Magnesium fluoride: Mg+2 + F-1  MgF2 “Switch and drop” the charges to make them subscripts, ignore the + or – signs. If a Mg atom gives away 2 e-, a fluorine atom can only take 1 e- at a time, so Mg needs to bond to 2 F atoms.

Formulas for Ionic Compounds Try it! Sodium and Oxygen Potassium and Chlorine Magnesium and oxygen Aluminum and oxygen Remember: assign charges first, then switch and drop!

Formulas for Ionic Compounds Try it! Sodium and Oxygen: Na+1 + O-2  Potassium and Chlorine: K+1 + Cl-1  Magnesium and oxygen: Mg+2 + O-2  Aluminum and oxygen: Al+3 + O-2  Remember: assign charges first, then switch and drop!

Formulas for Ionic Compounds Try it! Sodium and Oxygen: Na+1 + O-2  Na2O Potassium and Chlorine: K+1 + Cl-1  KCl Magnesium and oxygen: Mg+2 + O-2  MgO (reduce!) Aluminum and oxygen: Al+3 + O-2  Al2O3 Remember: assign charges first, then switch and drop!

Covalent Bonds Also called molecular bonds Formed between atoms that are sharing electrons Example: CH4  Characteristics of Covalent bonds & compounds Electrons are shared Usually between two nonmetals Weaker than ionic bonds Lower melting and boiling points Can have double bonds (sharing 2 e-) or triple bonds (sharing 3 e-) Can be polar or nonpolar

Covalent Bonds Sometimes covalent compounds share electrons equally, and sometimes they do not. Polar covalent – a covalent molecule that has an unequal sharing of electrons Example: H2O Nonpolar covalent – a covalent molecule that has an equal sharing of electrons Example: CH4 All the negativity (electrons) are toward one end of the molecule The electrons are equally spread out around the atom

Metallic Bonds Metallic bonds - A bond formed by the attraction between positively charged metal ions and the electrons around them Characteristics of metallic bonds Neighboring atoms in a sample of a metal packed together Electrons are free to move from atom to atom and the atoms can slide past each other easily This explains why metals conduct electricity and are able flexible

Ch 5 Sec 2 Quiz Matching: ____ bond formed between positively charged metal ions and the surrounding electrons ____ bond formed between oppositely charged ions ____ bond formed between atoms that share electrons A) Ionic B) Covalent C) Metallic

Ch 5 Sec 2 Quiz Matching: _C_ bond formed between positively charged metal ions and the surrounding electrons _A_ bond formed between oppositely charged ions _B_ bond formed between atoms that share electrons A) Ionic B) Covalent C) Metallic

Bellwork Get yourselves into exactly SIX groups. Each of you will have your own worksheet with your own responses. I will assign which column your group will be doing. After the allowed time period, you will share with us your information!

What will we be learning? Section 3: Compound Names and Formulas Name simple ionic and covalent compounds. Predict the charge of a transition metal cation in an ionic compound. Write chemical formulas for simple ionic compounds. Distinguish a covalent compound’s empirical formula from its molecular formula.

Ionic Compounds Name  Formula Formula  Name Assign the charges to the atoms, “switch and drop” Magnesium Fluoride  Mg+2 + F-1  MgF2 Formula  Name Name the metal first, then change the ending of the nonmetal to –ide Al2O3  Aluminum Oxide

Ionic Compounds w/Polyatomic Ions Name  Formula Assign the charges to the atoms, switch and drop Use parentheses around the polyatomic ion Aluminum hydroxide  Al+3 + (OH)-1  Al(OH)3 Formula  Name Name the metal first, and the polyatomic ion second Do NOT change any endings! Mg(SO4)  Magnesium Sulfate

Ionic Compounds w/Transition Metals The charges of transition metals can change You can determine the charge of the transition metal by looking at its formula and what it is bonded with REVERSE “switch and drop”! Fe2O3  Fe+3 + O-2 FeO  Fe+2 + O-2 Predict! What is the charge of the Cu if the formula is CuCl2?

Ionic Compounds w/Transition Metals The charges of transition metals can change You can determine the charge of the transition metal by looking at its formula and what it is bonded with REVERSE “switch and drop”! Fe2O3  Fe+3 + O-2 FeO  Fe+2 + O-2 Predict! What is the charge of the Cu if the formula is CuCl2? +2: Cu+2 + Cl-1  CuCl2

Ionic Compounds w/Transition Metals The charge of a transition cation can also be told to you using Roman numerals Copper(II) Sulfate  Cu+2 + SO4-2  CuSO4 Iron(III) Oxide  Fe+3 + O-2  Fe2O3

Covalent Compounds Prefix system is used to tell how many of each type of atom there are in the compound Change the ending to the second element to –ide N2O4  Dinitrogen tetroxide CO2  Carbon dioxide Boron trifluoride  BF3 # of atoms Prefix 1 Mono- 2 Di- 3 Tri- 4 Tetra- 5 Penta- 6 Hexa- 7 Hepta- 8 Octa- 9 Nona- 10 Deca-

Covalent Compounds Some compounds have a reduced formula and a non-reduced formula Empirical formula – simplest or reduced formula CH2O = Empirical formula Formaldehyde: CH2O Acetic Acid: C2H4O2 Glucose: C6H12O6

Ch 5 Sec 3 Quiz Which part of an ionic compound should be written first? How can you tell what the charge is of a transition metal? What kind of formula gives the numbers of atoms of each element in a compound in the simplest form?

Ch 5 Sec 3 Quiz Which part of an ionic compound should be written first? Cation, or the metal How can you tell what the charge is of a transition metal? Look at the molecular formula and what it is bonded with What kind of formula gives the numbers of atoms of each element in a compound in the simplest form? Empirical formula

Let’s Review! P 150 #1-5 (Section 1 Review) P 161 #1-4 (Practice) P 164 #1-6 (Section 3 Review)