II. Molecular Compounds

Covalent Bonding A major type of atomic bonding occurs when atoms share electrons.atoms As opposed to ionic bonding in which a complete transfer of electrons occurs,electrons

Covalent bonds Non metal + Non metal Example -Hydrogen + Hydrogen

Share electrons

A Shorthand Method for Drawing Covalent Bonds Straight lines can be used to represent a covalent bond between two atoms. Each line represents a shared pair of e -

Single bonds

O=C=O Carbon dioxide, CO 2 Double Bond

1.Draw a skeleton structure. a.Determine the central atom 1. Largest atom or C Rules for drawing Lewis structures 2. Count total valence electrons on all atoms a. If the molecule is charged, add an electron for each negative charge and subtract an electron for each positive charge 3. Connect the structure. a. Draw a bond between the central atom and each outside atom. Each bond uses 2 valence electrons. 4. Make outside atoms happy fill valence energy levels 5.Place all remaining electrons on the central atom. a. the octet on the central atom is not complete, try sharing lone pairs of outside atoms to form double or triple bonds

Lewis structures Draw a covalent bond for –H 2 0 –H –CH 4 –CO 2 –CO

Ch Chemical Bonds III. Naming Molecular Compounds  Molecular Names  Molecular Formulas

 Write the names of both elements.  Change the final ending to -ide.  Add prefixes to indicate subscripts.  Only use mono- prefix with oxide. A. Molecular Names

PREFIX mono- di- tri- tetra- penta- hexa- SUBSCRIPT A. Molecular Names

 CCl 4  N 2 O  SF 6 carbon tetrachloride dinitrogen monoxide sulfur hexafluoride A. Molecular Names

 Write the larger non metal first.  Add subscripts according to prefixes. B. Molecular Formulas

 phosphorus trichloride  dinitrogen pentoxide  dihydrogen monoxide PCl 3 N 2 O 5 H 2 O B. Molecular Formulas

 The Seven Diatomic Elements Br 2 I 2 N 2 Cl 2 H 2 O 2 F 2 B. Molecular Formulas

Ch. 6 & 7 - Chemical Bonding I. Bonding

A. Vocabulary 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

A. Vocabulary CHEMICAL FORMULA Molecular Formula Unit IONICCOVALENT CO 2 NaCl

A. Vocabulary ION Polyatomic Ion Monatomic Ion 1 atom 2 or more atoms NO 3 - Na +

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 B. Types of Bonds Physical State solid liquid or gas odorous

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

Ionic Bonding - Crystal Lattice RETURN B. Types of Bonds

Covalent Bonding - True Molecules RETURN B. Types of Bonds Diatomic Molecule

Metallic Bonding - “Electron Sea” RETURN B. Types of Bonds

C. Bond Polarity Most bonds are a blend of ionic and covalent characteristics. Difference in electronegativity determines bond type.

C. Bond Polarity Electronegativity –Attraction an atom has for a shared pair of electrons. –higher e - neg atom   - –lower e - neg atom   +

C. Bond Polarity Electronegativity Trend (p. 151) –Increases up and to the right.

Nonpolar Covalent Bond –e - are shared equally –symmetrical e - density –usually identical atoms C. Bond Polarity

++ -- Polar Covalent Bond –e - are shared unequally –asymmetrical e - density –results in partial charges (dipole)

zNonpolar zPolar zIonic View Bonding Animations.Bonding Animations C. Bond Polarity

Examples: Cl 2 HCl NaCl =0.0 Nonpolar =0.9 Polar =2.1 Ionic