1. Chapter 6 Ionic and Molecular Compounds
6.5 Molecular Compounds: Sharing Electrons
Learning Goal Given the formula of a molecular compound, write its correct name; given the name of a molecular compound, write its formula.

2. Molecular Compounds
A molecular compound contains two or more nonmetals that form a covalent bond.
Valence electrons are shared by nonmetal atoms in a covalent bond to achieve stability.
When two or more atoms share electrons, they form a molecule.

3. Formation of Hydrogen Molecule
In a hydrogen (H2) molecule,
two hydrogen atoms share electrons to form a covalent single bond
each H atom acquires two (2) electrons
each H becomes stable like the nearest noble gas, helium (He)

4. Formation of Hydrogen Molecule

5. Electron-Dot Formulas, Molecular Compounds
In an electron-dot formula also called a Lewis structure,
shared electrons or bonding pairs are shown as two dots or a single line between atoms
nonbonding pairs of electrons or lone pairs, are placed next to the atom

6. Diatomic Elements
The elements hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine exist as diatomic molecules in nature.

7. Sharing Electrons Between Atoms of Different Elements
Electron-dot formulas for molecules with different elements show
the order of bonded atoms in a covalent compound
the bonding pairs of electrons between atoms
the unshared (lone) valence electrons
a central atom with an octet

8. Sharing Electrons Between Atoms of Different Elements
The number of covalent bonds that a nonmetal atom forms is usually equal to the number of electrons it needs to acquire a stable electron configuration.

9. Electron-Dot Formulas, Molecular Compounds

10. Learning Check
State the number of valence electrons, bonding pairs, and nonbonding pairs for each of the following molecules.
Molecules
Valence electrons
Bonding pairs
Nonbonding pairs

11. Solution
State the number of valence electrons, bonding pairs, and nonbonding pairs for each of the following molecules.
Molecules
Valence electrons
Bonding pairs
Nonbonding pairs
1 + 7 = 8 1 3
5 + 3(7) = 26 10

12. Names and Formulas, Molecular Compounds
In molecular compounds, prefixes are used to indicate the number of nonmetals. The prefix mono is not used on the first nonmetal in the compound. NO2 is nitrogen dioxide. When vowels o and o or a and o appear together, the first vowel is omitted. CO is carbon monoxide.

13. Names and Formulas, Molecular Compounds

14. Common Molecular Compounds

15. Guide to Naming Molecular Compounds

16. Learning Check
Name the compound NCl3.

17. Solution
Name the compound NCl3.
Step 1 Name the first nonmetal by its elemental name.
In NCl3, the first nonmetal (N) is nitrogen.
Step 2 Name the second nonmetal by using the first syllable of its element name followed by ide.
The second nonmetal (Cl) is chloride.

18. Solution
Name the compound NCl3. Step 3 Add prefixes to indicate the number of atoms (subscripts). Because there is one nitrogen atom, no prefix is needed. The subscript 3 for the Cl atoms is written as the prefix tri. The name of NCl3 is nitrogen trichloride.

19. Writing Formulas from the Names of Molecular Compounds

20. Learning Check
Write the formula for the molecular compound, diboron trioxide.

21. Solution
Write the formula for the molecular compound, diboron trioxide. Step 1 Write the symbols in the order of the elements in the name. B O Step 2 Write any prefixes as subscripts. B2O3

22. Summary of Naming Ionic and Molecular Compounds

23. Learning Check
Name each of the following ionic or molecular compounds.
A. BF3
B. OCl2
C. Al2O3
D. Ni3PO4

24. Solution
Name each of the following ionic or molecular compounds.
A. BF3 boron trifluoride
B. OCl2 oxygen dichloride
C. Al2O3 aluminum oxide
D. Ni3PO4 nickel(I) phosphate