I Ionic Bonding A Definition transfer of electrons

I. Ionic Bonding A. Definition: transfer of electrons in forming bonds

B. Types of Ions 1. Cations - positively charged (an electron is lost) a. Monatomic ions - single-atoms example: Na+ and Ca++ b. Polyatomic ions - many-atomed example: ammonium, NH 4+

2. Anions - negatively charged (electrons gained) a. Monatomic ions - single-atoms examples: Cl-, O 2 -, P 3 b. Polyatomic ions - many-atomed example: PO 43 -, CO 32 -, SO 42 -

C. Octet Rule - atoms tend to gain, lose, or share electrons to complete an octet in their outer shells

D. Empirical Formula - simplest whole number ratio of atoms in a compound ( only formula fo an ionic compound, example: Na 100 Cl 100=Na. Cl)

II. Covalent Bonding A. Definition: sharing electrons to form a bond B. Molecule- simplest (smallest) unit of a covalent compound

C. Unshared Pair of Electrons- paired valence electrons, not involved in bonding

D. Multiple Bonds 1. double bond- four electrons shared between two atoms 2. triple bond - six electrons shared between two atoms

Exceptions to the Octet Rule Reduced valences- boron compounds (boron - six in outer shell) Expanded valences - phosphorus pentachloride

III. Naming Binary Compounds - compounds made of only two elements A. Write name of less electronegative element first B. Write the root of the second element followed by -ide

C. Ionic or Covalent 1. ionic: use a Roman numeral in parentheses to indicate the metal's charge Cs. I : cesium (I ) iodide 2. covalent: use prefixes to indicate the number of atoms of each element present PH 3 : phosphorus trihydride

IV. Ionic-Covalent Continuum A. DEN <. 4 B. . 4 < DEN < 2. 0 C. DEN > 2. 0 nonpolar covalent bond ionic bond

V. Energy changes in the formation of Compounds A. Ionic – exothermic (heat out): ionic compounds are formed exothermically 1) formation of positive ions (loss of electrons): endothermic 2) formation of negative ions (gaining electrons): exothermic 3) forming the crystal lattice ( attraction of opposites) exothermic

B. Covalent - either formed endothermically and unstable, or exothermically and stable

VI. Molecular Geometry and VSEPR Valence Shell Electron Pair Repulsion Theory

A. Bonding Regions and Shapes 1. 2. 3. 4. 5. 6. linear trigonal planar tetrahedral: (includes pyramidal and bent) trigonal bipyramid - results from expanded valence octahedral - results from expanded valence