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Learn about valence electrons, Lewis dot diagrams, octet rule, and more to understand ionic and covalent bonds. Practice oxidation numbers and valence electron calculations.
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Welcome! • Warm-up Please open the Socrative app on your phone and answer the two MC questions to the best of your ability (do not discuss it yet).
Reminders • 15 school days to Winter Break • 34 school days to End of 1st Semester [January 28th]
Until Then… What you can expect from me: -Clear delineation of assignments And due dates. -Availability before and after school -Sensitivity to other classes (proper notice) What I need from you: -Attentiveness to directions -Clarifying questions when material is unclear -Assignments turned in on time, complete *Incomplete work will be handed back *Work which ignores directions will be handed back
Chemical Bonding A Complicated Relationship
Today The Tools for Understanding Bonding • Valence Electrons • Lewis Dot Diagrams • The Octet Rule • Oxidation States
Why do we care? Ionic Bonds
Why do we care? Covalent Bonds
Valence Electrons He is an exception: 2 valence The “d” and “f” blocks do NOT count for valence
Lewis Dot Structures • Simplified way of showing only the highest energy (valence) electrons. • Will only ever have a maximum of 8 dots • All elements in the same group (column) will have the same Lewis dot diagram.
The Octet Rule • Electron Configuration is related to stability! Ne… 1s2 2s2 2p6 F… 1s2 2s2 2p5 • Noble Gases have 8e- in their highest E level, so they are perfectly happy to not react. • Everything else is trying to reach a more stable state, so electrons must either be donated or accepted in order to complete an octet How many bonds will “F” form?
Octet Rule • Bottom Line: Elements tend to gain or lose electrons in order to achieve the electron configuration of a noble gas (i.e. a full valence shell!) Exceptions: Hydrogen (H) and Helium (He) Because both are in the first E level (n=1) which only has 2 valence
2 Elements Bonded to Complete Octets Resulting e- Configurations It Was 1s2 2s2 2p6 3s1 1s2 2s2 2p6 3s2 3p5 Now it’s 1s2 2s2 2p6 1s2 2s2 2p6 3s2 3p6
Another, Less Obvious Example Resulting e- Configurations 1s2 2s1 It Was 1s2 2s2 2p5 1s2 Now it’s 1s2 2s2 2p6
- + Li+ Li Li+ Li 1s 2s 2p 1s 2s 2p F- + + F F F 1s 2s 2p 1s 2s 2p Ionic Bond [He] [Ne] 1s22s1 1s22s22p5 1s2 1s22s22p6
Oxidation Numbers The number of electrons gained or lost when forming compounds 0 +1 +2 +3 -3 -2 -1
Practice How many valence electrons does Beryllium (Be) have? 2 What does the dot diagram of Beryllium (Be) look like? How many electrons would Beryllium (Be) need to gain to have a full valence? 6 How many electrons would Beryllium (Be) need to lose to have a full valence? 2 What is the likely oxidation number of Beryllium (Be)? 2+
Practice How many valence electrons does Phosphorus (P) have? 5 What does the dot diagram of Phosphorus (P) look like? How many electrons would Phosphorus (P) need to gain to have a full valence? 3 How many electrons would Phosphorus (P) need to lose to have a full valence? 5 What is the likely oxidation number of phosphorus (P)? 3-
IF YOU CANNOT DETERMINE THE OXIDATION NUMBER, YOU WILL NOT UNDERSTAND OR BE ABLE TO COMPLETE IONIC BONDING FORMULAS!
Check Yourself! Before you wreck yourself • On a separate sheet of paper: • Write the oxidations number for N, Se, I, Cs, Ba, and Ca • We did not talk about group 4 oxidation numbers. List a possibility and justify it in one sentence
Warm-Up 12/1 How many valence electrons does bromine (Br) have? 7 What does the dot diagram of bromine (Br) look like? How many electrons would bromine (Br) need to gain to have a full valence? 1 How many electrons would bromine (Br) need to lose to have a full valence? 7 What is the likely oxidation number of bromine (Br)? 1-
Yesterday The Tools for Understanding Bonding • Valence Electrons • Lewis Dot Diagrams • The Octet Rule • Oxidation States
Today • Understand ionic bonds by constructing and writing proper formulas and compound names.
Ionic Bonding Activity • In groups of 2 to 3, you will receive a packet of ion cards. • Using the numbers on the board, count your cards and make sure you have the right number of each. • Follow the directions in the packet and answer the questions in detail (ask Mr. White for help). • The packet should be completed in class.
Ionic Bonds Ionic Bonding is a transfer of electrons from one atom to another.
Ionic Bonds Once a transfer of electron(s) occurs, the atoms become ions (charged), and are held together by the electrostatic force (the fact that opposite charges attract). Li+ F-
Ionic Bonds Usually occurs between a metal and a non-metal
Why? A large enough difference in electronegativity indicates an ionic bond, or said another way, one atom is pulling so hard on electron(s) that it is transferred completely.
Bottom Line Bond types are classified by the difference in electronegativity of the atoms involved
Example NaCl EN = 3.0 EN = .9 ΔEN = 3.0 - .9 = 2.1 Since the difference in EN is greater than 2.0, the bond is ionic
Ionic Compounds 1) Made up of cations (+ charged) and anions (- charged) 2) Correctly written compounds are electrically neutral (no overall charge)
Pieces of an Ionic Bond Anion- Negatively charged ion Cl- O2- N3- Cation- Positively charged ion Na+ Mg2+ B3+
Monatomic Ions • Have the same name as the elemental form • Exist as only atoms of a single element • First component in an ionic compound
Polyatomic Ions • Consist of atoms of more than one element • Come as a “package deal” when forming ionic compounds • Don’t get mixed up between the net charge of the ion and the individual charges
Formulas for Binary Compounds • Contain a monatomic cation (metal) and a monatomic anion (nonmetal) • Metal comes first • Non-metal comes second • The overall charge must be 0 • You can use subscipts (i.e. O2) to get the overall charge to zero. • DO NOT WRITE THE CHARGE IN THE COMPOUND
Thursday 12/3 • Please have out your worksheet (pink) from yesterday • You will need: • Notes • P. Table • Polyatomic Reference Sheet (from yesterday)
Today Rules for Systematically Naming Ionic Compounds: • Binary Compounds (Single cation, single anion) • Binary Compounds with “d” block elements (using roman numerals) • Polyatomic Compounds (with and without “d” block elements)
Rules Naming Binary Ionic Compounds Li2O • List the name of the cation first, and keep the name the way it is.
Rules Naming Binary Ionic Compounds Li2O • List the name of the cation first, and keep the name the way it is. Name: Lithium ………..
Rules Naming Binary Ionic Compounds Li2O • List the name of the cation first, and keep the name the way it is. Name: Lithium ……….. • List the name of the anion second, change the ending to “ide” if it is simply an element.
Rules Naming Binary Ionic Compounds Li2O • List the name of the cation first, and keep the name the way it is. Name: Lithium ……….. • List the name of the anion second, change the ending to “ide” if it is simply an element. Name: Lithium Oxide
Rules Naming Binary Ionic Compounds Li2O Full Name: Lithium Oxide
Examples with “d” block elements (transition metals) d block
Rules Naming Binary Ionic Compounds FeCl2 • List the name of the cation first, and keep the name the way it is.
Rules Naming Binary Ionic Compounds FeCl2 • List the name of the cation first, and keep the name the way it is.
Rules Naming Binary Ionic Compounds FeCl2 • List the name of the cation first, and keep the name the way it is. Name: Iron