1. Chapter 5 Compounds and Their Bonds
5.5 Covalent Compounds

2. Covalent Bonds Covalent bonds form
when atoms share electrons to complete octets
between two nonmetal atoms from from Groups 4A(14), 5A(15), 6A(16), and 7A(17)

3. Formation of H2 In the simplest covalent molecule, H2 , the H atoms
increase attraction as they move closer
share electrons
form a covalent bond

4. Formation of H2 (continued)

5. Forming Octets in Molecules
In a fluorine (F2) molecule, each F atom
shares one electron
acquires an octet

6. Diatomic Elements
These elements share electrons to form diatomic, covalent molecules.

7. Learning Check
What is the name of each of the following diatomic molecules?
H2 _______________
N2 _______________
Cl2 _______________
O2 _______________
I2 _______________

8. Solution What is the name of each of the following diatomic molecules?
H2 hydrogen
N2 nitrogen
Cl2 chlorine
O2 oxygen
I2 iodine

9. Carbon Forms 4 Covalent Bonds
In a methane (CH4) molecule,
the central C atom shares 4 electrons to attain an octet
each H atom shares 1 electron with the carbon atom to become stable like He

10. Electron-Dot Formula for NH3
In NH3, a N atom is bonded to three H atoms.
The electron-dot structure is written as:
Lone pair of electrons

11. Number of Covalent Bonds
The number of covalent bonds can be determined from
the number of electrons needed to complete an octet.

12. Electron-Dot Formulas and Models of Some Covalent Compounds

13. Guide to Writing Electron-Dot Formulas

14. Guide to Writing Electron-Dot Formulas
STEP 1 Determine the arrangement of atoms.
STEP 2 Determine the total number of valence electrons.
STEP 3 Attach each bonded atom to the central atom with a pair of electrons.
STEP 4 Place remaining electrons as lone pairs to complete octets (2 for H atoms).
STEP 5 If octets are not complete, form a multiple bond by converting a lone pair to a bonding pair.

15. Single and Multiple Bonds
In a single bond, one pair of electrons is shared.
In a double bond, two pairs of electrons are shared.
In a triple bond, three pairs of electrons are shared.

16. Electron-Dot Formula of CS2
Write the electron-dot formula for CS2.
STEP 1 Determine the atom arrangement. The C atom is the central atom.
S C S
STEP 2 Determine the total number of valence electrons for 1C and 2S.
1 C(4e–) S(6e–) = 16e–

17. Electron-Dot Formula of CS2 (continued)
STEP 3 Attach each S atom to the central C atom using one electron pair.
S : C : S
16e– – 4e– = 12e– remaining
STEP 4 Attach 12 electrons as 6 lone pairs.
: S : C : S :

18. Electron-Dot Formula of CS2 (continued)
To complete octets, form one or more multiple bonds.
Convert two lone pairs to bonding pairs between C and
S atoms to make two double bonds.

19. A Nitrogen Molecule has A Triple Bond
In a nitrogen molecule, N2,
each N atom shares 3 electrons
each N atom attains an octet
the sharing of 3 sets of electrons is a multiple bond called a triple bond

20. Resonance Structures Resonance structures are
two or more electron-dot formulas for the same arrangement of atoms
related by a double-headed arrow ( )
written by changing the location of a double bond between the central atom and a different attached atom

21. Writing Resonance Structures
Sulfur dioxide has two resonance structures.
STEP 1 Write the arrangement of atoms.
O S O
STEP 2 Determine the total number of valence electrons.
1 S(6e−) + 2 O(6e−) = 18e−
STEP 3 Connect bonded atoms by single electron pairs.
O : S : O e− used
18e− – 4e− = 14e− remaining

22. Writing Resonance Structures (continued)
STEP 4 Add 14 remaining electrons as 7 lone pairs.
STEP 5 Form a double bond to complete octets. Two resonance structures are possible.

23. Learning Check
FNO2, a rocket propellant, has two resonance structures. One is shown below. What is the other resonance structure?

24. Solution
FNO2, a rocket propellant, has two resonance structures. One is shown below. What is the other resonance structure?