INTRODUCTION TO BONDING CHEMICAL BONDING

CHEMICAL BOND ATTRACTIVE FORCE BETWEEN ATOMS OR IONS THAT BINDS THEM TOGETHER AS A UNIT BONDS FORM IN ORDER TO… DECREASE POTENTIAL ENERGY (PE) INCREASE STABILITY

BONDS ARE… FORCES THAT HOLD GROUPS OF ATOMS TOGETHER AND MAKE THEM FUNCTION AS A UNIT. TWO TYPES: 1) Ionic bonds – transfer of electrons (gained or lost; makes formula unit) 2) Covalent bonds – sharing of electrons. The resulting particle is called a “molecule”

TYPES OF BONDS IONIC COVALENT Bond Formation Type of Structure Solubility in Water Electrical Conductivity Other Properties e - are transferred from metal to nonmetal high yes (solution or liquid) yes e - are shared between two nonmetals low no usually not Melting Point crystal lattice true molecules Physical State solid liquid or gas odorous

TYPES OF BONDS “electron sea” METALLIC Bond Formation Type of Structure Solubility in Water Electrical Conductivity Other Properties Melting Point Physical State e - are delocalized among metal atoms very high yes (any form) no malleable, ductile, lustrous solid

KEEPING TRACK OF ELECTRONS ATOMS IN THE SAME COLUMN... 1)HAVE THE SAME OUTER ELECTRON CONFIGURATION. 2)HAVE THE SAME VALENCE ELECTRONS. THE NUMBER OF VALENCE ELECTRONS ARE EASILY DETERMINED. IT IS THE GROUP NUMBER FOR A REPRESENTATIVE ELEMENT GROUP 2A: Be, Mg, Ca, ETC. HAVE 2 VALENCE ELECTRONS

VALENCE ELECTRONS ARE…? THE s AND p ELECTRONS IN THE OUTER ENERGY LEVEL OR THE HIGHEST OCCUPIED ENERGY LEVEL. THE ELECTRONS RESPONSIBLE FOR THE CHEMICAL PROPERTIES OF ATOMS.

ELECTRON DOT DIAGRAMS ARE… A WAY OF SHOWING & KEEPING TRACK OF VALENCE ELECTRONS. HOW TO WRITE THEM? WRITE THE SYMBOL - IT REPRESENTS THE NUCLEUS AND INNER (CORE) ELECTRONS PUT ONE DOT FOR EACH VALENCE ELECTRON (8 MAXIMUM) THEY DON’T PAIR UP UNTIL THEY HAVE TO (HUND’S RULE) X

The Electron Dot diagram for Nitrogen 5 l Nitrogen has 5 valence electrons to show. l First we write the symbol. N l Then add 1 electron at a time to each side. l Now they are forced to pair up. We have now written the electron dot diagram for Nitrogen.

The Octet Rule l In Chapter 6, we learned that noble gases are unreactive in chemical reactions l In 1916, Gilbert Lewis used this fact to explain why atoms form certain kinds of ions and molecules l The Octet Rule: in forming compounds, atoms tend to achieve a noble gas configuration; 8 in the outer level is stable l Each noble gas (except He, which has 2) has 8 electrons in the outer level

OCTET RULE METALS LOSE ELECTRONS TO ATTAIN A NOBLE GAS CONFIGURATION. FORM CATIONS (POSITIVE) NONMETALS GAIN ELECTRONS TO ATTAIN NOBLE GAS CONFIGURATION. FORM ANIONS (NEGATIVE) AN ATOM IS ELECTRICALLY NEUTRAL BECAUSE THE PROTONS AND ELECTRONS ARE EQUAL, IONS FORM WHEN THEY LOSE OR GAIN ELECTRONS.

COMMON ION CHARGES NA IONIC NOMENCLATURE

IONIC FORMULAS WRITE EACH ION, CATION FIRST. DON’T SHOW CHARGES IN THE FINAL FORMULA. OVERALL CHARGE MUST EQUAL ZERO. IF CHARGES CANCEL, JUST WRITE SYMBOLS. IF NOT, USE SUBSCRIPTS TO BALANCE CHARGES. USE PARENTHESES TO SHOW MORE THAN ONE POLYATOMIC ION. STOCK SYSTEM - ROMAN NUMERALS INDICATE THE ION’S CHARGE.

IONIC NOMENCLATURE IONIC NAMES WRITE THE NAMES OF BOTH IONS, CATION FIRST. CHANGE ENDING OF MONATOMIC IONS TO -IDE. POLYATOMIC IONS HAVE SPECIAL NAMES. STOCK SYSTEM - USE ROMAN NUMERALS TO SHOW THE ION’S CHARGE IF MORE THAN ONE IS POSSIBLE. OVERALL CHARGE MUST EQUAL ZERO.

IONIC NOMENCLATURE CONSIDER THE FOLLOWING: DOES IT CONTAIN A POLYATOMIC ION? -IDE, 2 ELEMENTS  NO -ATE, -ITE, 3+ ELEMENTS  YES DOES IT CONTAIN A ROMAN NUMERAL? CHECK THE TABLE FOR METALS NOT IN GROUPS 1 OR 2. NO PREFIXES!

zpotassium chloride zmagnesium nitrate zcopper(II) chloride K + Cl  Mg 2+ NO 3  Cu 2+ Cl   KCl  Mg(NO 3 ) 2  CuCl 2 IONIC NOMENCLATURE

zNaBr zNa 2 CO 3 zFeCl 3 sodium bromide sodium carbonate iron(III) chloride IONIC NOMENCLATURE

CHEMICAL BONDING MOLECULAR COMPOUNDS

LEWIS STRUCTURES OCTET RULE MOST ATOMS FORM BONDS IN ORDER TO OBTAIN 8 VALENCE E - FULL ENERGY LEVEL STABILITY ~ NOBLE GASES Ne

++ -- ++ LEWIS STRUCTURES NONPOLAR COVALENT - NO CHARGES POLAR COVALENT - PARTIAL CHARGES

MOLECULAR NOMENCLATURE PREFIX SYSTEM (BINARY COMPOUNDS) 1.LESS E - NEG ATOM COMES FIRST. 2.ADD PREFIXES TO INDICATE # OF ATOMS. OMIT MONO- PREFIX ON FIRST ELEMENT. 3.CHANGE THE ENDING OF THE SECOND ELEMENT TO -IDE.

PREFIX MONO- DI- TRI- TETRA- PENTA- HEXA- HEPTA- OCTA- NONA- DECA- NUMBER MOLECULAR NOMENCLATURE

zCCl 4 zN 2 O zSF 6 carbon tetrachloride dinitrogen monoxide sulfur hexafluoride MOLECULAR NOMENCLATURE

zarsenic trichloride zdinitrogen pentoxide ztetraphosphorus decoxide AsCl 3 N2O5N2O5 P 4 O 10 MOLECULAR NOMENCLATURE

NOF Cl Br I H MOLECULAR NOMENCLATURE THE SEVEN DIATOMIC ELEMENTS BR 2 I 2 N 2 CL 2 H 2 O 2 F 2