Covalent CompoundsCovalent Compounds

Covalent BondsCovalent Bonds Atoms of two nonmetals combinedAtoms of two nonmetals combined Held together by sharing electrons Held together by sharing electrons

““co” means cooperate/shareco” means cooperate/share ““valent” refers to the valence electronsvalent” refers to the valence electrons

Atoms bonded with covalent bonds are called Atoms bonded with covalent bonds are called moleculesmolecules

Covalent moleculesCovalent molecules

Atoms with covalent Atoms with covalent bonds share electrons bonds share electrons to achieve an octet for to achieve an octet for

each of themeach of them Some elements exist Some elements exist

in nature as in nature as diatomic moleculesdiatomic molecules

= molecules that = molecules that contain two like contain two like

atomsatoms* Note the names* Note the names

Sharing Electrons Between Sharing Electrons Between Atoms of Different ElementsAtoms of Different Elements

The number of The number of electrons that an electrons that an atom shares and atom shares and the number of the number of covalent bonds it covalent bonds it forms are usually forms are usually equalequal to the to the number of number of electrons needed electrons needed to acquire a noble to acquire a noble gas arrangementgas arrangement

ExceptionsExceptions 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 7AH

1 bond

B3 bonds

C4 bonds

N3 bonds

O 2 bonds

F1 bond

Si 4 bonds

P3 (or 5) bonds

S2 (4 or

6)bonds

Cl, Br, I1 (3 or

5)Bonds

Multiple Covalent BondsMultiple 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

Naming Covalent Naming Covalent CompoundsCompounds

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 fornaming covalent

numbers used incompounds

1 Mono

2 Di

3 Tri

4 Tetra

5 Penta

6 Hexa

7 Hepta

8 Octa

9 Nona

10 Deca

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

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

Naming and Writing FormulasNaming 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

Naming and Writing FormulasGuidelines for Naming

1) Confirm the compound is a molecular compound (2 nonmetals)

2) Omit mono- when the the formula contains only one of the first element in the name

3) 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

Naming and Writing FormulasPractice

Write the name of these molecular compounds:

a) NCl3

b) BCl3

c) NI3

d) SO3

e) N2H4

f) N2O3

Naming and Writing FormulasPractice

Write the formulas for these binary molecular compounds:

a) Phosphorus pentachloride

b) Iodine heptafluoride

c) Chlorine trifluoride

d) Iodine dioxide

e) Carbon tetrabromide

f) Diphosphorus trioxide

Summary of naming rulesSummary of naming rulesBinary 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 compoundnonmetal = 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

Organic CompoundsOrganic Compounds