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CHAPTER 12: CHEMICAL BONDING KEY
12.2 IONIC BOND
Example: Draw the electron-dot symbols representing the following reactions:
sodium atom + chlorine atom form ions to produce sodium chloride
Na + Cl → Na+^ [ Cl ]-
12.3 COVALENT BOND
Ex: Use electron dot formulas to represent the reaction described.
hydrogen atom + chlorine atom → HCl molecule
H + Cl → H Cl
1 2.4 ELECTRON DOT FORMULAS OF MOLECULES
Example: Draw the Electron dot formula for each of the following molecules:
a. H 2 S c. SO (^3)
Valence e- = 2x1 + 6 = 8 e- Valence e- = 6 + 3x6 = 24 e-
electron pairs = 8/2 = 4 pairs electron pairs = 24/2 = 12 pairs
b. CH 2 Br 2 d. HCN Valence e- = 4 + 2x1 + 2x7 = 20 e- Valence e- = 1+ 4 + 5 = 10 e- electron pairs = 20/2 = 10 pairs electron pairs = 10/2 = 5 pairs
S
H
H S O
O
O
C Br H C N
Br
H
H
12.4 ELECTRON DOT FORMULAS OF POLYATOMIC IONS
E xample: Draw the Electron dot formula for each of the following polyatomic ions:
a. NH 4 +^ c. PO 4 –
Valence e- = 5 + 4x1 – 1 = 8 e- Valence e- = 5 + 4x6 + 3 = 32 e-
electron pairs = 8/2 = 4 pairs electron pairs = 32/2 = 16 pairs
b. NO 3 –^ d. CO 3 2–
Valence e- = 5 + 3x6 + 1 = 24 e- Valence e- = 4 + 3x6 + 2 = 24 e-
electron pairs = 24/2 = 12 pairs electron pairs = 24/2 = 12 pairs
12.9 SHAPES OF MOLECULES
Ex. Give the electron dot formula, shape, and bond angles for CO (^2)
Valence e- = 4 + 2x6 = 16 e- electron pairs = 16/2 = 8 pairs
shape: linear angles: 180°
Ex. Give the electron dot formula, shape, and bond angles for CH 2 O
Valence e- = 4 + 2x1 + 6 = 12 e- electron pairs = 12/2 = 6 pairs
H C O AB 3 shape: trigonal planar angles: 120° H
Ex. Give the Electron dot formula, shape, and bond angles for CH 4.
Valence e- = 4 + 4x1 = 8 e- electron pairs = 8/2 = 4 pairs
H
H C H AB 4 Tetrahedral angles: 109.5°
H
MOLECULES WHERE CENTRAL ATOM HAS ONE OR MORE LONE PAIRS
AB 2 E: bent ⇒ central atom is bonded to two outer atoms (B) and has a lone pair of electrons (E)
N O
O
O
C O
O
O
P O
O
N H
H
H
H
O
O -
O C^ O AB^2
ii. shape of CH 2 F 2 : tetrahedral ii. shape of OF 2 : bent iii. bond angles in CH 2 F 2 : 109.5° iii. bond angles in OF 2 : <109.5°
C. phosphite ion, PO 3 –
Electron dot formula
Valence e- = 5 + 3x6 + 3 = 26 e- electron pairs = 26/2 = 13 pairs
ii. shape of PO 3 –3^ : trigonal pyramid
iii. bond angles in PO 3 –3^ : <109.5°
12.6 POLAR COVALENT BONDS
Example: For each of the bonds below: i. Use delta notation (δ and δ – ) to indicate which atom is more electronegative, and ii. Use an arrow to point from the less electronegative atom to the more electronegative atom. δ+^ δ −^ δ+^ δ −^ δ+^ δ − C-Cl N—O H—O
Example: Identify the type of bond described for each of the following:
A. ionic bond: metal-nonmetal C. polar covalent: 2 different nonmetals B. metallic bond: metal D. nonpolar covalent: 2 same nonmetals
C i. The C–O bonds in CO 2. D iv. The C–C bonds in C 3 H 8
D ii. The bonds in F 2. B v. The bonds in Ba.
A iii. The bonds in K 2 O. C vi. The bonds in H 2 O.
O F
F
C F
F
H
H AB 4 AB 2 E
P O
O
O
12.9 SHAPES OF MOLECULES
A molecule with polar bonds is polar if either of the following applies:
- the central atom has one or more lone pair(s) of electrons, or
- the atoms bonded to the central atom are not identical
Ex. 1: Determine whether the following molecules are polar or nonpolar:
CO 2 : nonpolar - no lone pairs on C H 2 O: polar – O (the central atom)
and same outer atoms has 2 lone pairs of e-
O C O O
H
H
SO 3 nonpolar – no lone pairs on S and same outer atoms
S
O
O
O
Ex. 2: Determine whether the following molecules are polar or nonpolar:
CCl 4 CHCl
H
nonpolar - outer atoms are the same and
no lone pairs on central atom
polar – outer atoms are different
