Naming Covalent (Molecular) Compounds

Naming Covalent (Molecular) Compounds

Covalent Bonds

• Occurs between non-metals

• Instead of taking or giving electrons, non-metals will share them with each other

• Bonds can be: single, double, or triple

Non-Polar Vs. Polar Covalent Bonds

• Non-Polar Covalent: The electrons are shared equally between the two atoms

• Polar Covalent: The electrons are shared unequally between the two atoms

Covalent Bonds

• As we said before covalent bonds occur between non-metals only

• The image to the left show all the non-metals that can be found in a covalent molecule

• The light blue column at the end are the Nobel Gases and they don't form bonds with a few exceptions.

• The rest of the periodic table are mostly metals with a small group of semi-metals

Multiple Choice

Which element is a non-metal?

• sulfur

• potassium

• copper

• sodium

Multiple Choice

Which compound below is only made up of non-metals?

• N₂O₂

• NaCl

• LiOH

• HMnO₄

Diatomic Molecules

There are 7 elements that exist in nature as diatomic molecules.

What elements exist as diatomic molecules?

H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂  

HONCl BrIF

HOBr FINCl

Multiple Choice

Which of the elements below is NOT a diatomic molecule?

• hydrogen

• helium

• chlorine

• nitrogen

Binary Covalent Compounds

• Binary covalent compounds are between 2 different nonmetals.

Binary Covalent Compounds (Con't)

• Nonmetals can share electrons in many different ways. This means that two nonmetals can create multiple compounds together.

• Each of these contains a different ratio of elements. Because of this, we have to make sure that the name of the compound explains the correct ratio.

To show the correct ratio of elements, we use prefixes.

NOTE!!!!

• Once you decide if a compound is ionic or covalent you know whether or not to use prefixes.

• Only COVALENT COMPOUNDS use PREFIXES!

  
  

Steps for Naming

Binary Covalent Compounds

Rules for Using Prefixes

• Rule 1: Prefixes are only for BINARY COVALENT compounds.

• Rule 2: The prefix mono- is never used on the first element of a binary covalent compound.  Without a prefix it is assumed that there is only 1.

• Example: CO2 is carbon dioxide, and NOT monocarbon dioxide.

• Rule 3: Remove the -o or -a from a prefix before adding it to oxide. 

• Example: CO is carbon monoxide, and NOT carbon monooxide.

Fill in the Blank

What is the name of the following compound: CS₂?

Fill in the Blank

What is the name of the following compound: N₂Cl₄?

Fill in the Blank

What is the name of the following compound: PBr₅?

Because of the prefixes, it is very easy to go from the name of a binary covalent compound to its formula.

Multiple Choice

What is the correct formula for disulfur hexafluoride

• SF

• S₂F

• S₂F₆

• S₆F₂

Multiple Choice

What is the correct formula for iodine heptafluoride?

• IF₅

• IF₆

• IF₄

• IF₇

Multiple Choice

What is the correct formula for the compound dinitrogen monoxide?

• NO

• NO₂

• N₂O

• N₂O₂