1. Covalent Compounds

2. Covalent Bonds Atoms of two nonmetals combined
Held together by sharing electrons
“co” means cooperate/share
“valent” refers to the valence electrons
Atoms bonded with covalent bonds are called molecules

3. Covalent molecules
Atoms with covalent bonds share electrons to achieve an octet for each of them
Some elements exist in nature as diatomic molecules
= molecules that contain two like atoms
* Note the names

4. Sharing Electrons Between Atoms of Different Elements
The number of electrons that an atom shares and the number of covalent bonds it forms are usually equal to the number of electrons needed to acquire a noble gas arrangement

5. Exceptions
Although the nonmetals typically form octets,…
Some (P, S, Cl, Br, and I) can share more valence electrons and form stable valence shells of 10 or 12 electrons 1A 3A 4A 5A 6A 7A H
1 bond B
3 bonds C
4 bonds N O
2 bonds F Si P
3 (or 5)
bonds S
2 (4 or 6)
Cl, Br, I
1 (3 or 5)
Bonds

6. Multiple Covalent Bonds
In many covalent compounds, atoms may share 2 or 3 pairs of electrons to complete their octets
Double bond  2 pairs of e- shared
Triple bond  3 pairs of e- shared
C, O, N, and S are most likely to form multiple bonds
Atoms of hydrogen and the halogens do not form double or triple bonds

7. Naming Covalent Compounds
1st nonmetal uses its elemental name
2nd nonmetal uses its elemental name with the –ide ending
Subscripts are expressed as prefixes placed in front of each name
Prefixes for
naming covalent
numbers used in
compounds 1
Mono 2 Di 3
Tri 4
Tetra 5
Penta 6
Hexa 7
Hepta 8
Octa 9
Nona 10
Deca

8. Ex) carbon + oxygen can form CO (carbon monoxide) or
The names of covalent compounds need prefixes because several different compounds can be formed from the same two nonmetals
Ex) carbon + oxygen can form
CO (carbon monoxide) or
CO2 (carbon dioxide)
In the name of a covalent compound, the prefix mono is usually omitted on the 1st atoms name
When the vowels o and o or a and o appear together, the first vowel is omitted

9. Practice naming covalent compounds
Name each of the following covalent compounds:
a) NCl3 b) N2O4
Nitrogen trichloride Dinitrogen tetroxide
Write the formula of sulfur dichloride.
SCl2

10. Naming and Writing Formulas
Naming Binary Molecular Compounds
The prefix tells how many atoms of each element are present in each molecule of the compound
Carbon Monoxide vs. Carbon Dioxide
Mono- indicates one oxygen
Di- indicates two oxygens

11. Naming and Writing Formulas
Guidelines for Naming
Confirm the compound is a molecular compound (2 nonmetals)
Omit mono- when the the formula contains only one of the first element in the name
Add -ide to the second element in the formula
Guidelines for Formula Writing
1) Use the prefixes in the name to tell you the subscripts in the formula

12. Naming and Writing Formulas
Practice
Write the name of these molecular compounds:
NCl3
BCl3
NI3
SO3
N2H4
N2O3

13. Naming and Writing Formulas
Practice
Write the formulas for these binary molecular compounds:
Phosphorus pentachloride
Iodine heptafluoride
Chlorine trifluoride
Iodine dioxide
Carbon tetrabromide
Diphosphorus trioxide

14. Summary of naming rules
Binary Compounds (may be ionic or covalent) 
State the 1st element, followed by the 2nd element with an –ide ending
If 1st element is 
a metal = ionic compound
nonmetal = covalent compound
Ionic compounds 
Is the 1st able to form more than one ion? …
…if so, use Roman numerals to indicate charge
Compounds with polyatomic ions use –ate or –ite endings (determined by # of oxygens)
* Exception NH4+ written 1st
Covalent compounds 
Prefixes are needed to show # of atoms of each nonmetal in the formula

15. Organic Compounds