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Examples and exercises on chemical bonding, focusing on ionic and covalent bonds, and electron dot formulas for various molecules and polyatomic ions. Students will learn how to represent reactions using electron dot symbols, determine the number of valence electrons and electron pairs, and identify the shapes and bond angles of molecules.
What you will learn
Typology: Exams
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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
C Br H C N
Br
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
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 C H AB 4 Tetrahedral angles: 109.5°
H
AB 2 E: bent ⇒ central atom is bonded to two outer atoms (B) and has a lone pair of electrons (E)
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 molecule with polar bonds is polar if either of the following applies:
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-
SO 3 nonpolar – no lone pairs on S and same outer atoms
Ex. 2: Determine whether the following molecules are polar or nonpolar:
nonpolar - outer atoms are the same and
no lone pairs on central atom
polar – outer atoms are different