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Chemical Bonding: Ionic, Covalent, and Electron Dot Formulas, Exams of Chemistry

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

  • How do you represent ionic reactions using electron dot symbols?
  • How do you determine the shape and bond angles of a molecule using electron dot formulas?
  • What is the difference between ionic and covalent bonds?

Typology: Exams

2021/2022

Uploaded on 09/27/2022

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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. H2S c. SO3
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. CH2Br2 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
N
H
C Br
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. NH4+ c. PO4–3
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
CHM 130 Chapter 12 page 1 of 5
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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:

  1. the central atom has one or more lone pair(s) of electrons, or
  2. 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