Chemical Bonding

Chemical Bonds / Formulas Atoms bond to become “happy” – octet rule When they bond they form compounds. Each compound has a special formula Subscripts show how many of each element is in the compound

FORMULAS MgCl2 The subscript is the number at the bottom of a formula. There is 1- Mg & 2 – Cl Never use 1 as a subscript!

IONIC BOND formed between two ions by the transfer of electrons

Formation of Ions from Metals Ionic compounds result when metals react with nonmetals Metals lose electrons to form a positive charge Nonmetals gain electrons to form a negative charge Metals: Nonmetals: Na+ N -3 Ca+2 S -2 Al+2 Br -

IONIC BONDS Bonds form from the (+) & (-) charges. Form a network of ions. Form strong bonds. Conduct electricity when melted or dissolved in water.

Writing Ionic Formulas – binary Magnesium & chlorine Write the metal ion Mg +2 Write the nonmetal ion Cl - If charges DO NOT cancel – drop & swap MgCl2 Calcium & oxygen Write the metal ion Ca +2 Write the nonmetal ion O -2 If charges cancel – ratio is 1:1 ( 1 of each) CaO

Transition Metals – d & f block Ion charges change – an element can have more than one ion charge The charge is given as a ROMAN NUMERAL Ex: Iron (II) Fe+2 / Iron (III) Fe+3 Gold (I) Au + / Gold (III) Au+3 You will not have to memorize all the charges each transition metal forms – the charges will be given to you !!!!!

Practice Magnesium & iodine Iron (III) & bromine Barium & nitrogen Aluminum & phosphorus

Naming Ionic Formula - binary Transition Metals Name the metal & Include the charge using a Roman Numeral Change the ending of the nonmetal ending to –ide Ex: Fe +2 Cl - iron (II) chloride Au + O -2 gold (I) oxide Representative Metals Name the metal Change the ending of the nonmetal to – ide Ex: MgCl2 - magnesium chloride AlP - aluminum phosphide

Practice FeCl3 Ni3N ZnO FeS CaBr2 Na3N BCl3 MgO

Ternary Ionic Bonds – contain Polyatomic Ions Polyatomic ion : a group of (covalently) bonded nonmetals that form a charge. Act as a single ion in an ionic bond Have special names that DO NOT CHANGE You need to write down the polyatomic ions and their names on an index card and DO NOT LOSE IT!!! You will use your list on all quizzes and tests!

Ammonium NH4+ Acetate C2H3O2- Hypochlorite ClO- Chlorite ClO2- Chlorate ClO3- Perchlorate ClO4- Cyanide CN- Hydroxide OH- Nitrite NO2- Nitrate NO3- Bicarbonate/Hydrogen Carbonate HCO3- Carbonate CO3-2 Chromate CrO4-2 Dichromate Cr2O7-2 Oxalate C2O4-2 Sulfate SO4-2 Sulfite SO3-2 Phosphite PO3-3 Phosphate PO4-3 Permanganate MnO4- Peroxide O2-2

Writing Ionic Formulas - ternary Write the cation – all metals (only polyatomic cation is ammonium: NH4+ ) Write the anion – all nonmetals and polyatomic ions If charges cancel – 1:1 ratio If charges DO NOT cancel – drop & swap You must use parenthesis if more than one polyatomic ion is present

Naming Ionic Formulas- ternary Cation Representative metals- element name Transition (D-block) metals- element name and a Roman numeral to show charge Polyatomic ion (NH4+)- regular name Anion Polyatomic ion- regular name Nonmetal- change ending to -ide Ex: NaNO3- sodium nitrate Cu2(SO4)3- copper (III) sulfate NH4Cl- ammonium chloride

Practice Iron(III) chlorite cesium nitrate Zinc(II) nitrite Gold(III) carbonate Silver(I) phosphite Copper(I) acetate cesium nitrate barium sulfite aluminum hydroxide strontium phosphate ammonium sulfide

COVALENT BOND bond formed by the sharing of electrons

Covalent compounds result when nonmetals bond with nonmetals Both nonmetals share their valence electrons to be happy – Octet Rule Examples: CO2 SCl2 H2O CH4

Naming Covalent formulas Use prefixes to show the # of atoms of each element in a covalent compound 1 – mono 6 - hexa 2 – di 7 - hepta 3 – tri 8- octa 4 – tetra 9 - nona 5 – penta 10 – deca 1st element – use prefixes only of the # of atoms is greater than 1 2nd element – use prefixes; change ending to – ide

Practice carbon dioxide trinitrogen octafluoride CO2 N3F8 Se4Br9 S7O carbon dioxide trinitrogen octafluoride tetraselenium nonabromide heptasulfur monoxide

Writing Covalent formulas Use the prefix to identify how many of each nonmetal atoms are in each molecule The prefix becomes the subscript. Carbon Tetrahydride Disulfur Hexachloride CH4 S2Cl6

1) Name the following covalent compounds: a) SiF4 b) N2S3 c) H3Br7 d) S5Br9 e) H2O Write the formulas for the following covalent compounds: a) diboron hexahydride b) nitrogen tribromide c) sulfur hexachloride d) diphosphorus pentoxide

Drawing Structures- Ionic Electrons are TRANSFERRED Practice: NaBr AlCl3

Drawing Structures- Covalent Electrons are SHARED 1 pair= single bond 2 pairs= double bond 3 pairs= triple bond Dot formulas and Structural formulas

Covalent Structure Practice H2O CH4 CO2 Cl2 O2 N2

Diatomic Molecules H2, N2, O2, F2, Cl2, Br2, I2 Always pair up with themselves in a pure sample Allows them to be stable when there are no other elements to bond with H2, N2, O2, F2, Cl2, Br2, I2

Metallic Bonds Formed between two metals One or two valence electrons (usually transition metals) strong positive nuclei pull atoms close together, causing the outer e- orbitals to overlap electrons delocalize; creates a ‘sea of electrons’ electrons flow freely between atoms, this is why metals are good conductors of electricity

The remaining slides are for HONORS CHEMISTRY only

VSEPR Valence Shell Electron Pair Repulsion Predicts shapes of covalently bonded molecules Copy the chart on p.263 of your book

Coordinate Covalent Bonds one atom contributes both bonding electrons once formed, no different from other bonds, just different source of electrons

Coordinate Covalent Ex: Chlorate, ClO3-

Resonance Structures shifting of electron pairs/bonds without shifting atoms

Resonance Ex: Carbonate, CO3-2 Ozone, O3