Part 1: Covalent BondsAnd Molecules

Objectives

• Explain what a covalent bond is and what type of elements form them

• Describe how molecules with covalent bonds are named

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Octet Rule

• Atoms want to achieve a noble gas electron configuration – s2p6 – 8 valence electrons in dot structure

• Exception is hydrogen wants to have two valence electrons to be like helium (“duet rule”)

Ionic Compounds• Ex.) NaCl• Na achieves octet rule by losing 1

electron and Cl achieves octet rule by gaining 1 electron

• Valence electrons get transferred from metal to nonmetal

• Ionic compounds contain ions (cation + anion) held together by ionic bonds

• Some nonmetals are unlikely to lose or gain electrons

• Ex. Nonmetal elements in Group 4 have four electrons in their outer levels

• To gain or lose four electrons is highly unlikely due to their protons’ attraction

Covalent Bonds

Molecular Compounds

• Ex.) H2O• No ions!!!• All atoms are held together by

covalent bonds• Electrons get shared so the octet

rule can be met for all atoms• Two non-metals

• The stable attraction that forms between nonmetal atoms when they share electrons is known as a covalent bond • The neutral particle that forms due to electron sharing is called a molecule

• Use Lewis Dot structures for clarity

Covalent Bonds

A water molecule

• A single covalent bond is made up of two shared electrons

• A water molecule containstwo single bonds in which each atom contributes one electron to the other in the bond• The result: a stable outer energy level for each atom in the molecule:

• 2 for H and 8 for O

Covalent Bonds

Molecule Example (water)

Molecule- Smallest part of molecular compound held together by covalent bonds

• A covalent bond also can contain more than one pair of electrons

• An example of this is the bond in oxygen (O2) or nitrogen (N2)

Covalent Bonds

Molecular Formula

Structural Formula

Molecule Representation

H2O

Naming Molecular (Covalent) Compounds

• No molecular compounds will ever contain metals or contain ions

• You need to forget about charges when naming molecular compounds

Rules for Naming Molecular Compounds

1. Use full name of first element2. Second element uses the “root” name of

the element + the “ide” suffix. 3. Use hydrate prefixes to denote how many

atoms of each are in the compound.Ex.) CO2 = Carbon dioxide

4. Prefix “mono” is never used in front of the 1st element and the 2nd element only uses the prefix “mono” if it is oxygen. Ex.) carbon monoxide

Examples of Naming Molecules…

• OF2

• CO• NH3

• P2I5

• H2O

• Oxygen difluoride• Carbon monoxide NOT

monooxide• Nitrogen trihydride• Diphosphorus pentiodide (drop

“a” from penta)• Dihydrogen monoxide

• NONE OF THESE COMPOUNDS CONTAIN METALS!!!

• HYDROGEN = NOT A METAL!!!

Objectives

• Explain what a covalent bond is and what type of elements form them

• Describe how molecules with covalent bonds are named

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