Explains chemical bonding **More good stuff available at: www.wsautter.com and http://www.youtube.com/results?search_query=wnsautter&aq=f

1. Copyright Sautter 2015

2. Cl
H
CHEMICAL BONDS
BONDS HOLD ATOMS
TOGETHER TO
FORM MOLECULES
2

3. TYPES OF CHEMICAL BONDS
•(1) IONIC BONDS - ELECTRONS AS TRANSFERRED
FROM METALS TO NONMETALS (IONIC SALTS FOR
EXAMPLE NaCl, CaCl2)
•(2) COVALENT BONDS – ELECTRONS ARE SHARED
BETWEEN NONMETALS (DIATOMIC MOLECULES
FOR EXAMPLE THE HALOGENS, F2, Cl2, etc.)
•(3) COORDINATE COVALENT BONDS – A BONDING
PAIR OF ELECTRONS IS CONTRIBUTED BY ONLY
ONE ATOM IN THE BOND (FOR EXAMPLE
AMMONIUM ION, NH4
+, HYDRONIUM ION, H3O+)
3

4. WHY DO BONDS BETWEEN ATOMS FORM ?
• WHEN BONDS FORM THE STABILITY OF THE COMBINED
ATOMS INCREASES AS COMPARED TO THAT OF THE
INDIVIDUAL ATOMS. GENERALLY CHEMICAL
STABILITY IS RELATED TO THE ABILITY OF ATOMS TO
ATTAIN THE ELECTRON CONFIGURATION OF AN INERT
GAS. FOR MANY ATOMS THIS MEANS ACQUIRING
EIGHT ELECTRONS IN THE OUTER SHELL. THIS IS
CALLED AN “OCTET” STRUCTURE.
• THE EXCEPTATIONS ARE SMALLER ATOMS (LIKE
HYDROGEN, LITHIUM, BERYLLIUM, ETC.) THESE
ATTEMPT TO ACQUIRE TWO ELECTRONS LIKE HELIUM.
• RECALL THE TERM “ISOELECTRONIC”. ATOMS
ATTEMPT TO BECOME ISOELECTRONIC WITH THE
NEAREST INERT GAS.
4

5. +9
+19
2e
1e
8e
18e
7e
2e
8e
IONIC BOND FORMATION - ELECTRON
TRANSFER BETWEEN METALS & NONMETALS
ISOELECTRONIC
WITH Ar
ISOELECTONIC
WITH Ne
5

6. REPRESENTING ATOMS AND MOLECULES
USING ELECTRON DOT FORMULAE
(LEWIS DOT REPRESENTATIONS)
• LEWIS DOT FORMULAE USE THE ATOMIC
SYMBOL TO REPRESENT THE “KERNEL” OF THE
ATOM THAT IS THE NUCLEUS AND ALL INNER
ENERGY LEVEL ELECTRONS. DOTS ARE THEN
USED TO REPRESENT EACH OUTER ENERGY
LEVEL ELECTRON (VALENCE ELECTRONS)
• THE PAIRING OF THESE ELECTRON “DOTS”
APPROXIMATES THE PAIRINGS OF ELECTRONS IN
ATOMIC AND MOLECULAR (BONDING) ORBITALS
OF THE ATOM OR MOLECULE.
6

7. ELECTRON DOT REPRESENTATIONS
FOR SOME COMMON ATOMS
(LEWIS DOT NOTATIONS)
7

8. COMMON PROPERTIES AND
CHARACTERISTICS OF COVALENT BONDS
• COVALENT BONDS MAY BE SINGLE, DOUBLE OR
TRIPLE BONDS
• (1) SINGLE BOND – ONE PAIR OF BONDING
ELECTRONS JOINS TWO ATOMS TOGETHER
• (2) DOUBLE BOND – TWO PAIRS OF BONDING
ELECTRONS JOIN TWO ATOMS TOGETHER (OCCURS
PRIMARILY WITH CARBON, OXYGEN, NITROGEN
AND SULFUR)
• (3) TRIPLE BOND – THREE PAIRS OF BONDING
ELECTRONS JOIN TWO ATOMS TOGETHER (OCCURS
PRIMARILY WITH CARBON AND NITROGEN)
8

9. COVALENT BONDING
(ELECTRON SHARING – SINGLE BOND)
+9
+9
2e
7e
7e
2e
6e
6e
BOTH ISOELECTRONIC
WITH Ne 9

10. COVALENT BONDING
(ELECTRON SHARING – DOUBLE BOND)
+8
+8
2e
6e
6e
2e
4e
4e
BOTH ISOELECTRONIC
WITH Ne 10

11. COVALENT BONDING
(ELECTRON SHARING – TRIPLE BOND)
+7
+7
2e
5e
5e
2e
2e
2e
BOTH ISOELECTRONIC
WITH Ne 11

12. ELECTRON DOT REPRESENTATIONS OF
POLYATOMIC MOLECULES AND IONS
WRITING THE DOT FORMULA FOR METHANE - CH4
STEP I – DETERMINE THE TOTAL NUMBER OF
VALENCE ELECTRONS FOR ALLATOMS.
CARBON (C) HAS 4 VALENCE ELECTRONS
HYDROGEN (H) ATOMS HAVE 1 VALENCE ELECTRON
FOR EACH OF THE FOUR ATOMS (4 x 1 = 4)
THE TOTAL NUMBER OF VALENCE ELECTRONS = 8
STEP II-SELECT THE CENTRAL ATOM (THE ONE THAT
CAN FORM THE GREATEST NUMBER OF BONDS)
AND PLACE THE OTHER ATOMS SYMMETRICALLY
AROUND IT. 12

13. WRITING THE DOT FORMULA FOR METHANE CH4
STEP III -PLACE TWO DOTS (ELECTRONS)
BETWEEN EACH BONDED PAIR OF ATOMS.
STEP IV -FILL IN OCTET STRUCTURES FOR ANY
REMAINING ATOMS UNTIL ALL THE ELECTRONS
ARE USED.*(HYDROGEN, BERYLLIUM & BORON ARE
COMMON EXCEPTATIONS TO THE OCTET RULE)
OCTET (8)
FOR CARBON
HYDROGEN
REQUIRES
ONLY 2
ELECTRONS
13

14. WRITING THE ELECTRON STRUCTURE FOR
MONOCHLOROETHENE - C2H3Cl
2 C = 2 x 4 = 8 e
3 H = 3 x 1 = 3 e
1 Cl = 1 x 7 = 7 e
TOTAL VALENCE ELECTRONS =18
8 ELECTRONS
REMAIN
COMPLETE
OCTET FOR
CHLORINE
2 ELECTRONS
STILL REMAIN
PLACE THEM
TO COMPLETE
THE OCTETS
FOR BOTH
CARBONS
OCTETS
COMPLETE
DOUBLE BOND
14

15. WRITING ELECTRON DOT REPRESENTATIONS FOR
POLYATOMIC IONS CONTAINING RESONANCE
STRUCTURES (CARBONATE ION - CO3
-2 )
1 C = 1 x4 = 4 e
3 O = 3 x 6 = 18 e
-2 CHARGE = 2 e
TOTAL VALENCE ELECTRONS = 24
18 ELECTRONS
REMAIN
COMPLETE
THE OCTETS
ALL ELECTRONS ARE
USED BUT AN OCTET
FOR CARBON MUST
BE CREATED
-2
RESONANCE BOND
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