COVALENT
BONDING
I. INFORMATION TO
KNOW BEFORE YOU
BOND
• A. VALENCE ELECTRONSTHE ELECTRONS AVAILABLE
TO BE LOST, GAINED, OR
SHARED IN THE FORMATION
OF CHEMICAL COMPOUNDS
• B. ELECTRONEGATIVITY
– 1. A PROPERTY OF ATOMS IN
COMPOUNDS
– 2. MEASURE OF THE ABILITY OF
AN ATOM IN A CHEMICAL
COMPOUND TO ATTRACT
ELECTRONS
– 3. SCALE DEVISED BY LINUS
PAULING
– 4. FLUORINE IS 4.0 AND ALL OTHER
ELEMENTS ARE BASED ON IT.
II. COVALENT
BONDING
A. DEFINITION
•RESULTS FROM
THE SHARING OF
ELECTRON PAIRS
BETWEEN TWO
ATOMS.
B. TYPES OF COVALENT
BONDS
1. ELECTRONEGATIVITY WILL
TELL YOU WHETHER A BOND IS
IONIC OR COVALENT.
2. BONDS WITH
ELECTRONEGATIVITY
DIFFERENCES OF 1.7 OR LESS
HAVE 50% IONIC CHARACTER
AND ARE CONSIDERED
COVALENT.
3. TWO TYPES OF COVALENT
BONDS
a. NONPOLAR COVALENT- BONDING
ELECTRONS ARE SHARED EQUALLY,
RESULTING IN A BALANCE OF
ELECTRICAL CHARGE.
b. POLAR COVALENT- BONDED
ATOMS HAVE AN UNEQUAL
ATTRACTION FOR THE SHARED
ATOMS.
C. VOCABULARY THAT
GOES WITH COVALENT
BONDING
1. MOLECULE- NEUTRAL GROUP
OF ATOMS THAT ARE HELD
TOGETHER BY COVALENT
BONDS
2. MOLECULAR COMPOUNDCHEMICAL COMPOUND WHOSE
SIMPLEST UNITS ARE
MOLECULES
3. CHEMICAL
FORMULAINDICATES THE RELATIVE
NUMBERS OF ATOMS OF
EACH KIND IN A
CHEMICAL COMPOUND BY
USING ATOMIC SYMBOLS
AND NUMERICAL
SUBSCRIPTS
4. MOLECULAR FORMULASHOWS THE TYPES AND
NUMBERS OF ATOMS
COMBINED IN A SINGLE
MOLECULE OF A
MOLECULAR COMPOUND
5. DIATOMIC MOLECULE- A
MOLECULE CONTAINING
ONLY TWO ATOMS
D. FORMATION OF A
COVALENT BOND
1. NATURE FAVORS CHEMICAL
BONDING BECAUSE ATOMS
ARE AT A LOWER POTENTIAL
ENERGY WHEN BONDED TO
OTHER ATOMS THAN THEY
ARE AS INDEPENDENT
PARTICLES.
2. IN OTHER WORDS, THEY ARE
MORE STABLE.
E. CHARACTERISTICS OF
THE COVALENT BOND
1. COVALENTLY BONDED ATOMS
HAVE A CHARACTERISTIC BOND
DISTANCE.
2. BOND DISTANCE- THE DISTANCE
BETWEEN TWO BONDED ATOMS AT
THEIR MINIMUM POTENTIAL
ENERGY, THAT IS, THE AVERAGE
DISTANCE BETWEEN TWO BONDED
ATOMS
3. BOND ENERGY- THE ENERGY
REQUIRED TO BREAK A
CHEMICAL BOND AND FORM
NEUTRAL ISOLATED ATOMS
4. BOND ENERGY IS USUALLY
REPORTED IN KILOJOULES PER
MOLE (kJ/mol)
5. BOND LENGTHS AND ENERGIES
VARY DEPENDING ON WHAT
TYPE OF ATOMS ARE INVOLVED
F. THE OCTET
RULE
1. NOBLE GASES EXIST BY
THEMSELVES IN NATURE
BECAUSE THEY ARE AT
THEIR LOWEST POTENTIAL
ENERGY.
2. THIS IS DUE TO THEIR
ELECTRON CONFIGURATION
3. NOBLE GASES HAVE
COMPLETELY FILLED OUTER
s AND p ORBITALS.
4. THIS GIVES THEM 8
ELECTRONS IN THESE
ORBITALS WITH THE
EXCEPTION OF HELIUM
WHICH IS STABLE WITH A
FILLED OUTER s LEVEL AND 2
ELECTRONS.
5. OTHER ELEMENTS
WILL BECOME STABLE
IF THEY SHARE, LOSE,
OR GAIN ELECTRONS TO
GET THESE NOBLE GAS
CONFIGURATIONS.
6. OCTET RULE- CHEMICAL
COMPOUNDS TEND TO
FORM SO THAT EACH
ATOM, BY GAINING,
LOSING, OR SHARING
ELECTRONS, HAS AN
OCTET OF ELECTRONS IN
ITS HIGHEST OCCUPIED
ENERGY LEVEL
7. EXCEPTIONS TO THE
OCTET RULE
a. MOST MAIN GROUP ELEMENTS
WILL FOLLOW THE OCTET RULE
b. EXCEPTIONS:
i. HYDROGEN 2 ELECTRONS
ii. BORON6 ELECTRONS
iii. FLUORINE, OXYGEN, AND
CHLORINE MAY CAUSE
EXPANDED VALENCE. THIS
INVOLVES d ORBITALS.
G. ELECTRON-DOT
NOTATION
1. AN
ELECTRON-CONFIGURATION
NOTATION IN WHICH ONLY THE
VALENCE ELECTRONS OF AN
ATOM OF A PARTICULAR
ELEMENT ARE SHOWN,
INDICATED BY DOTS PLACED
AROUND THE ELEMENT’S
SYMBOL.
H. LEWIS STRUCTURES
1. ELECTRON DOT NOTATION USED
TO REPRESENT MOLECULES.
2. FORMULAS IN WHICH ATOMIC
SYMBOLS REPRESENT NUCLEI AND
INNER-SHELL ELECTRONS, DOTPAIRS OR DASHES BETWEEN TWO
ATOMIC SYMBOLS REPRESENT
ELECTRONS IN COVALENT PAIRS,
AND OTHER DOTS REPRESENT
LONE PAIRS.
I. MULTIPLE
COVALENT BONDS
1. SOME ELEMENTS WILL
SHARE MORE THAN ONE
ELECTRON PAIR (OXYGEN,
CARBON, NITROGEN)
2. DOUBLE BOND- 2 ELECTRON
PAIRS ARE SHARED
TRIPLE BOND- THREE
ELECTRON PAIRS ARE
SHARED
4. DOUBLE AND TRIPLE
BONDS HAVE HIGHER
BOND ENERGY AND ARE
SHORTER THAN SINGLE
BONDS.
3.