Nature of Covalent Bonding Part 1: Single Covalent Bonds

Objectives Describe how electrons are shared to form covalent bonds and identify exceptions to the octet rule Describe how electrons are shared to form covalent bonds and identify exceptions to the octet rule Demonstrate how electron dot structures represent shared electrons Demonstrate how electron dot structures represent shared electrons

Important Vocabulary Single covalent bond Single covalent bond Structural formula Structural formula Unshared pair Unshared pair Double covalent bond Double covalent bond Triple covalent bond Triple covalent bond Coordinate covalent bond Coordinate covalent bond Polyatomic ion Polyatomic ion Bond dissociation energy Bond dissociation energy Resonance structure Resonance structure

Octet Rule in Covalent Bonding In forming covalent bonds, electron sharing usually occurs so that atoms attain the electron configurations of noble gases In forming covalent bonds, electron sharing usually occurs so that atoms attain the electron configurations of noble gases Combinations of atoms of nonmetallic elements in groups 4A, 5A, 6A, & 7A are likely to form covalent bonds Combinations of atoms of nonmetallic elements in groups 4A, 5A, 6A, & 7A are likely to form covalent bonds For example, hydrogen has 1 electron For example, hydrogen has 1 electron Thus it will form a covalent bond with itself to share 2 electrons and attain the noble gas configuration of helium Thus it will form a covalent bond with itself to share 2 electrons and attain the noble gas configuration of helium

Single Covalent Bonds Form when two atoms are held together by sharing a pair of electrons Form when two atoms are held together by sharing a pair of electrons Of the diatomic molecules: hydrogen, chlorine, fluorine, bromine & iodine form single covalent bonds Of the diatomic molecules: hydrogen, chlorine, fluorine, bromine & iodine form single covalent bonds An electron dot structure such as H:H represents the shared pair of electrons of the covalent bond by two dots An electron dot structure such as H:H represents the shared pair of electrons of the covalent bond by two dots The pair of shared electrons forming the covalent bond is also represented as a dash H ‒ H The pair of shared electrons forming the covalent bond is also represented as a dash H ‒ H

Single Covalent Bonds

Structural Formulas Represent the covalent bonds by dashes Represent the covalent bonds by dashes Shows the arrangement of covalently bonded atoms Shows the arrangement of covalently bonded atoms

Unshared Pair An unshared pair is a pair of valence electrons that are not shared between atoms An unshared pair is a pair of valence electrons that are not shared between atoms It is also called a lone pair of a nonbonding pair It is also called a lone pair of a nonbonding pair For example: in the water molecule oxygen has 2 unshared pairs of electrons and forms 2 single covalent bonds For example: in the water molecule oxygen has 2 unshared pairs of electrons and forms 2 single covalent bonds

Unshared Pair Examples Identify the unshared pairs in the pictures below There are none

Drawing Lewis Structure for Simple Molecules Step 1: draw the symbols for the molecule side by side, leaving space for the dots Step 1: draw the symbols for the molecule side by side, leaving space for the dots Step 2: place two dots, one on top of the other, between the two symbols to represent the single covalent bond Step 2: place two dots, one on top of the other, between the two symbols to represent the single covalent bond Step 3: Add remaining number electrons for both symbols! Step 3: Add remaining number electrons for both symbols!

Examples H Cl H-F H:H :Cl:Cl: H:F:

Practice Problems #1 FIH-Cl