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Collected today: Ions Practice worksheet I should already have your Week 13 Homework

Why are we doing this? Elements in your life? What are most things made of? Atoms and ions combine to make compounds. (December, January…) Compounds combine and react to make new compounds. (Next semester)

Bonding

Electronegativity How strongly an atom attracts other electrons in a chemical bond Increases going up a group In lower periods, valence electrons are further from the nucleus, less “pull” from the protons Increases going across a period Electrons on the same energy level are more strongly “pulled” by the nucleus Same as ionization energy!!

Atomic Radius Increases Atomic Radius Increases

Electronegativity Increases Electronegativity Increases

chemical bond: strong electronic attraction between atoms decreases the potential energy of an atom; makes it more stable only the valence electrons are involved!

Three Types of Bonds Bond type depends on electronegativity (e-neg) Ionic Bond: very different e-negs. one metal, one non-metal Covalent Bond: both e-negs. very high two non-metals Metallic Bond: both e-negs. low one or more metals

Non-metals Metals

Anions Cations

High E-neg Low E-neg

Ionic Bond 1 from here 1 from here

Covalent Bond ≥2 from here

Metallic Bond ≥1 from here

Ionic Bonds metal + non-metal Low e-neg. + high e-neg. Transfer e- from one atom to another. Form cation + anion Ions are attracted to one another

sodium and chlorine Cl Na sodium transfers its electron to chlorine

Ionic or Covalent Bond? Na and Cl O and F Ca and Cl Mg and Br N and O Al and I O and P K and O

Ionic vs. Covalent Bonds: Modeling

Ionic Bond Vocabulary

Chemical formula: shows the kind and number of atoms in the smallest unit of the compound. Ex: H2O, NaCl, C6H12O6

Law of Definite Proportions: In any chemical compound, the masses of the elements are in the same proportions. Ex: If you had 100.00 g of magnesium sulfide, you would always have 43.13 g of magnesium and 56.87 g of sulfur. Magnesium chloride always has 1 atom of Mg to 2 atoms of chlorine.

Structure of Ionic Compounds: Crystal Lattice or Array LOTS and LOTS of ions all attracted to one another Ex: Salt = NaCl One Na atom for every Cl atom in a huge lattice

Formula unit: The formula for an ionic compound. The lowest whole-number ratio of ions in the compound. Ex: NaCl = 1:1 ratio of sodium to chlorine Ex: MgCl2 = 1:2 ratio of magnesium to chlorine

Writing Formulae for Ionic Compounds

Homework

Polyatomic ions: most covalently bonded, but have an overall electronic charge

Naming Ionic Compounds anion ending …ide Cr(OH)3 CuF2 Ca2+ PO43- chromium(III) hydroxide copper(II) fluoride Ca3(PO4)2 calcium phosphate

Crystal Lattice (Array) structure of an ionic bond each anion is surrounded by cations and vice versa

Announcements Missing work on spreadsheet on yellow bulletin board  Progress Reports submitted Friday only if your grade is… Failing Increased by 10% or more  Decreased by 10% or more 

Properties of Ionic Compounds hard brittle (break easily) solid high melting/boiling points do not conduct electricity as solids conduct electricity when dissolved in water (aq) or molten (melted into a liquid) - electrolyte more soluble in water than in other solvents

Ionic Compunds with Transition Metals

Transition Metals

Transition Metals Transition Metals: metals in groups 3-12 Can form ions with different charges Ex: Copper Cu+ Cu2+ Ex: Iron Fe2+ Fe3+

How do you know which ion is formed? Stock System: Indicates which charge a transition metal ion has Uses Roman Numerals to show charge I = 1+ II = 2+ III = 3+ IV = 4+ V = 5+

Oxidation States (Ions) of V http://www.youtube.com/watch?v=j-EaUHa_nuk&feature=PlayList&p=7E0E03ABA98A34AD&playnext=1&playnext_from=PL&index=19

http://www. youtube. com/watch http://www.youtube.com/watch?v=j-EaUHa_nuk&feature=PlayList&p=7E0E03ABA98A34AD&playnext=1&playnext_from=PL&index=19

Some hints: Stock system is ONLY used for cations that are transition metals Cu, Fe, Hg, Pb, Sn, Cr, Mn, Co Roman numeral comes AFTER cation. Anions NEVER have Roman numerals.

Examples

Covalent Bonding two or more non-metals atoms share some valence electrons (not transfer)

Covalent Bonding two or more non-metals atoms share some valence electrons (not transfer) single covalent bond: shares one pair of electrons double: 2 pairs of e- triple: 3 pairs of e-

Each e- donate by each atom usually each atom donates (gives) one of each pair of electrons dative covalent bond: sometimes one atom donates both electrons Electron Pair Shared by both atoms Each e- donate by each atom F F

octet rule: usually, atoms want 8 valence e- (H, He need 2) number of bonds formed depends on the number of e- required to fill the valence shell noble gases = full valence, rarely form compounds octet rule: usually, atoms want 8 valence e- (H, He need 2)

Ex: C has 4 valence e- Ex: F has 7 valence e- Nitrogen? needs 4 more to form a full octet C forms 4 bonds Ex: F has 7 valence e- needs 1 more to form a full octet F makes one bond Nitrogen?

F C F F F C F F C F F F F Bonding between C and F structural hybrid Lewis formula diagram diagram =e- pair F e- C e- =covalent bond

O C O O C O O C O Double Bond sharing two pairs of electrons bonds more strongly than a single bond structural hybrid Lewis O C O O C O O C O

Triple Bond Strongest N N N N N N

Drawing molecule diagrams Decide how many bonds each atom makes. The central atom is the one that makes the most bonds. Draw with single bonds Calculate remaining electrons Use remaining electrons

HCN (hydrogen cyanide) HCO2- (methanoate ion)

Draw structural, hybrid and Lewis structures HF NH3 CH4 CF4 NO2- CHCl3 NH4+ H2CO SeF2

“…those sciences are vain and full of errors that are not born of experience, the mother of all certainty.” Leonardo da Vinci

Length and Strength of Bonds single double triple longest shortest lowest energy highest energy

Covalent Molecules covalent bonds = strong forces between molecules = weaker covalent molecules are easily separated from one another soft solids do not conduct electricity more soluble in non-polar solvents than in water low melting/boiling points (liquid or gas at r.t.p.)

sometimes, a solid lattice is held together with covalent bonds covalent network (giant covalent structures): very hard, very high melting/boiling points Examples: diamonds and graphite (both C), SiO2