Chapter 5 Atoms and Bonding DO NOW: 1. Make a cover page in your NB for Chapter 5. 2. Draw a Bohr diagram for sulfur. 3. How many valence electrons does sulfur have? Chapter 5 Atoms and Bonding

Do Now: Draw a Bohr diagram for sulfur Do Now: Draw a Bohr diagram for sulfur. How many valence electrons does S have? Elements 1 - 20 1st level = 2 2nd level = 8 3rd level = 8 4th level = 2 Electron Shell Capacities: 16 P 16 N Elements 21 – 112 1st level = 2 2nd level = 8 3rd level = 18* 4th level = 32* 5th level = 32* *sub-levels exist Sulfur 16 electrons 6 valance electrons

All atoms want to achieve a full octet; which means they have a full outer valence shell Neon 10 electrons 8 valence electrons Ne

Why Do Valence Electrons Matter? The valence electrons show WHY certain elements bond with other elements to form compounds. H H S Sulfur’s 6 valence electrons WANT 2 more electrons 2 Hydrogen atoms will make 8 total

Remember, the # of valance electrons matches its family # Alkaline Earth Metals Alkali Metals Nitrogen Family Oxygen Family Carbon Family Halogens Noble Gases Boron Family Transition Metals *Matches 2nd digit groups 13 -18

Electron Dot Diagrams AKA Lewis Structure Symbol of an element surrounded by “dots”. Each dot represents one valence electron.

Electron Dot Diagrams AKA Lewis Structure The Element Symbol serves as the representation of the nucleus. C

Electron Dot Diagrams AKA Lewis Structure Dots are added at 12 o’clock, 3 o’clock, 6 o’clock, and 9 o’clock. C Carbon has only 4 electrons in the 2nd energy level so we need only represent those 4

Electron Dot Diagrams AKA Lewis Structure Only valence electrons are shown. Maximum of 8 dots (electrons)

Draw Electron Dot Diagrams for Lewis Structure Practice Oxygen Group = Valance electrons = Chlorine Group = Valance electrons = 16 17 6 7 O Cl Draw Electron Dot Diagrams for Beryllium and Sulfur

To Become Stable Atoms… They Bond Beryllium = Group 2 = 2 valance electrons Sulfur = Group 16 = 6 valance electrons

Chemical Bonds Atoms with unfilled valence shells are considered unstable. Atoms will try to fill their outer shells by bonding with other atoms. The number of valence electrons will determine how many bonds the atom can form. A chemical bond is the force that holds the molecules together Two types of bonds we will discuss: Ionic bonds Covalent bonds

Chemical Bonds are represented with Chemical Formulas Understanding chemical formulas: BaF2 Subscripts: tells how many atoms of that element are in the compound refers only to the element preceding it The subscript 2 in this formula is for the F (fluorine) Ba (barium) only has one atom (1’s are not written)

Al(NO3)3 Parentheses: The subscript outside the parentheses refers to all the elements inside the parentheses Multiply the subscript outside with each subscript inside to get the total number of atoms In this example there are: one Al (aluminum), three N (nitrogen), and nine O (oxygen) atoms 3BaF2 Coefficients: refers to each element that follows Multiply the coefficient with all subscripts The 3 in this example means there would be 3 Ba (barium) and 3 F2 (a total of 6 fluorine) atoms

Identifying and Counting Atoms in a Chemical Formula

Try It: Count the Atoms in each Chemical Formula

Try It: Count the Atoms in each Chemical Formula 1 12 6 1 2 42 24 1 1 6 4 22 21 9 4 6 12

Back to Bonding…

Valence Electrons Determine Oxidation Numbers +1 +4 -4 +2 +3 -3 -2 -1

Oxidation Numbers Shows the number of electrons an atom will gain, lose, or share. Positive (+) or negative (-) number assigned to an element. Comes from its family number on the Periodic table Metals (Families 1, 2, 13  +1, +2, +3) Nonmetals (Families 15, 16, 17  -3, -2, -1) Noble Gases (Family 18  0) Transition metals have various oxidation numbers between 1 and 4

+1 +4 -4 +2 +3 -3 -2 -1

Atoms that are no longer neutral are called ions An atom or groups of atoms that have lost or gained electrons Atom becomes either negatively (-) or positively (+) charged Change occurs since the ratio of protons to electrons is not equal

Ions form from atoms who gain or lose electrons

When an atom loses an electron it becomes positively charged Cation: positive ion When an atom loses an electron it becomes positively charged Ex: Calcium ion = Ca+2 Anion: negative ion When an atom gains an electron it becomes negatively charged Ex: Fluorine ion = F– (the 1 is inferred) Oxygen at the Playground

Polyatomic Ions + Ions that stay together as a group ammonium nitrate Poly- ionic name: ammonium nitrate +

Polyatomic Ions + Ions that stay together as a group ammonium nitrate Poly- ionic name: ammonium nitrate +

Time to Bond Ions Each index card represents either a cation (+) or an anion (-) Any opposite charged ions can bond Writing the chemical formula and names: 1. Oxidation numbers will become subscript numbers for the opposite element 2. Write both element names, but change the second element ending to “ide” Oxygen at the Playground

Ionic Bonding How does it work? Ionic bonding takes place between metals and non-metals. In an ionic bonds : oppositely charged ions (+) and (-) attract electrons are transferred Ex. NaCl (Na +1 Cl -1)

Naming Ionic Compounds Name of the + ion comes first, and - ion comes second Metal + Nonmetal Monatomic ions: change nonmetal ending to –ide Ex: Mg +2 + F -1 becomes MgF2 or Magnesium Fluoride Polyatomic ions: change nonmetal ending to –ate or –ite Ex: NaNO3 = sodium nitrate Mg3(PO4)2 = magnesium phosphate

I I Mg Do Now Magnesium +2 Iodine -1 1. Draw the Lewis structure for: 2. Write the chemical formula these two ions would create MgI2 (Magnesium Iodide) 3. What type of bond would these 2 atoms make? Ionic since Magnesium is Metal and Iodine is a Nonmetal I I Mg

Covalent Bonding H O H Occurs between two nonmetals Electrons are shared instead of being transferred Both atoms need to gain electrons, so they share the electrons they have. Atoms still follow the octet rule No ionic charges or oxidation numbers Sharing electron H O H Sharing electron - - - + - - + + - - - - -

How Covalent Bonding Works Electrons move back and forth between the outer energy levels of each atom. Each atom has a stable outer energy level some of the time. Atoms can share one, two, or three pairs of electrons. BrainPop Bonding Bonding Animation

Carbon Dioxide (CO2) Water (H2O) Nitrogen (N2) Double Bonds Share 4 Electrons Triple Bonds Share 6 Electrons Single Bonds Share 2 Electrons

Naming Covalent Compounds 1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca Each element gets a “greek prefix” Prefix refers to # of atoms in the molecule Change ending to “ide” Ex: N2O4 = dinitrogen tetroxide The first vowel is often dropped to avoid the combination of “ao” or “oo”. octaoxide = octoxide Exception: drop mono for first element CO2 = carbon dioxide CO = carbon monoxide

NOW do you find this funny?!

Try This: CCl4 P2O3 IF7 CCl4 = carbon tetrachloride Name these covalent compounds: CCl4 P2O3 IF7 CCl4 = carbon tetrachloride P2O3 = diphosphorus trioxide IF7 = iodine heptafluoride

Try This: Write the covalent compound formula: Tricarbon pentoxide Sulfur nonafluorine Tricarbon pentoxide = C3O5 Sulfur nonafluorine = SF9

Candy Bonds Activity

Today’s Agenda Candy Bonds activity Discuss/Correct HW worksheets from last week: Elemental Love Story Naming practice Complete Chapter 5 review worksheet Check answers in back- flower folder Share Answers to Candy Bonds * If time: Draw Your Own- plain white paper

1. What type of bond occurs between a metal and a nonmetal? ionic 2. What type of bond occurs between a two nonmetals? Covalent 3. CaF2 Calcium fluoride (*ionic) 4. triphosphorus tetrabromide P3Br4 5. N5O9 Pentanitrogen nonoxide

Solutions: Name these compounds: CCl4 = carbon tetrachloride P2O3 = diphosphorus trioxide IF7 = iodine heptafluoride Write these compounds: Tricarbon pentoxide = C3O5 Sulfur nonafluorine = SF9 What Kinds of Bonds are These?

Sodium Chloride = NaCl = Na+1 + Cl-1 Ionic Bonding Sodium Chloride = NaCl = Na+1 + Cl-1