Bonding

Why do atoms bond?

Atoms bond to get 8 valence electrons! Octet Rule: atoms need 8 valence electrons to be

stable.

2 ways to get 8

1. transfer electrons (forms ions)

2. Share electrons

Ionic bonding

Covalent bonding

Ionic Bonds (Review)

-Atoms lose or gain electrons electrons to become stable (like a noble gas)

-occurs between a metal and non-metal

-occurs between a positive ion and negative ion

Covalent Bonds

-Atoms share electronsshare electrons to become stable (like a noble gas)

-occurs between 2 non-metals

-covalent compounds are called moleculesmolecules

Which of the following are molecular and which are ionic?

NaBr CO2 O3 NO KCl AlBr3

Ionic

Molecular

Ionic

Molecular

Ionic Ionic

Covalent Bonding

2 Types of Covalent Bonds

Nonpolar covalent- electrons are shared equallyequally

Polar Covalent- electrons shared unequallyunequally

Naming and Writing Formulas of

Covalent Compounds

Polar Bonds

-have a partial negative charge on the more electronegative atom

-have a partial positive charge on the less electronegative atom

Nomenclature

Since electrons are shared two elements can bond in different ratios

Ex.: CO Carbon monoxide

CO2

We name covalent (molecular) compounds using prefixes to indicate the number of atoms of each.

Carbon dioxide

Prefixes

1 atom *mono- 6 atoms2 atoms 7 atoms3 atoms 8 atoms4 atoms tetra- 9 atoms5 atoms 10 atoms

hexa- di- hepta-tri- octa-

nona- penta- deca-

* Mono- is only used for the second element

Nomenclature:1) Name the first element that appears in the formula.

2) Name the second element that appears in the formula, changing its ending to –ide.

1. N2O

4

* There are 2 nitrogen atoms and 4 oxygen atomsName: dinitrogen tetraoxide

2. NOnitrogen monoxide

Naming Molecular CompoundsNaming Molecular Compounds

ExamplesNO₂

As₂O5

PCl₃

CCl₄

Nitrogen dioxide

Diarsenic pentoxide

Phosphorous trichloride

Carbon tetrachloride

Writing Formulas for Covalent Compounds

-Prefixes tell you subscripts for elements!

Ex.:

1. Nitrogen trioxide

Nitrogen has no prefix so there is 1 atom of nitrogen

The prefix tri- means there are 3 oxygens

Formula: NO3

Examples

dihydrogen monoxide

sulfur hexafluoride

xenon trioxide

tetraphosphorus trisulfide

H2O

SF6

XeO3

P4S3