Binary compoundsBinary compounds

Chapter 6 part IChapter 6 part I

Chemical FormulasChemical Formulas

Chemical formulas Chemical formulas inform as to the inform as to the type of elements type of elements that make up the that make up the compound and in compound and in what ratios.what ratios.

Chemical formulas Chemical formulas describe both ionic describe both ionic compounds and compounds and molecules.molecules.

Example:Example: HH22O: 2 hydrogens O: 2 hydrogens

for every 1 oxygenfor every 1 oxygen This is a molecule.This is a molecule. CaClCaCl22: 2 chlorines : 2 chlorines

for each calcium.for each calcium. This is an ionic This is an ionic

compound.compound.

Molecular formulasMolecular formulas

Molecular formulas Molecular formulas have 2 nonmetals have 2 nonmetals bound together.bound together.

Molecules are held Molecules are held together by sharing together by sharing electrons, not by electrons, not by charge.charge.

Hydrogen is a Hydrogen is a nonmetal!!nonmetal!!

Formula UnitsFormula Units

Chemical formulas Chemical formulas for ionic compounds for ionic compounds are called formula are called formula units.units.

Each unit is part of Each unit is part of a larger structure.a larger structure.

Consist of a metal Consist of a metal and a nonmetal.and a nonmetal.

They are held They are held together by charge.together by charge.

Ions and valence electronsIons and valence electrons

To write chemical formulas one To write chemical formulas one needs to understand how these needs to understand how these elements combine.elements combine.

Electrons are the key!Electrons are the key! Valence electrons (outer shell Valence electrons (outer shell

electrons) may be determined by the electrons) may be determined by the group on the periodic table. group on the periodic table.

Lewis dotLewis dot

The number of valence electrons is The number of valence electrons is represented by dots outside the atomic represented by dots outside the atomic symbol.symbol.

Hydrogen has one valence electron and Hydrogen has one valence electron and therefore one dot.therefore one dot.

Lithium has one valence electron and Lithium has one valence electron and therefore one dot therefore one dot

Berylium would have two dots and so on.Berylium would have two dots and so on. These are the same numbers as found in These are the same numbers as found in

the representative elements.the representative elements.

Lewis DotLewis Dot

Practice Lewis Practice Lewis Dot on your Dot on your worksheet.worksheet.

What happens What happens to the number to the number of dots if the of dots if the element forms element forms an ion?an ion?

Ionic compounds and Lewis DotIonic compounds and Lewis Dot

When Ions lose an When Ions lose an electron they have electron they have a complete shell, a complete shell, but they have a but they have a charge.charge.

These charged ions These charged ions are attracted to the are attracted to the opposite charge opposite charge forming salts.forming salts.

Molecular Bonding and Lewis DotMolecular Bonding and Lewis Dot

Except for H and He, how many Except for H and He, how many electrons do the elements in a electrons do the elements in a molecule want around them?molecule want around them?

ss22pp66 8 electrons to mimic the noble 8 electrons to mimic the noble gases.gases.

This is called the octet rule. Octet=8This is called the octet rule. Octet=8

Bonding and Lewis DotBonding and Lewis Dot

Double bonds and Double bonds and single bonds are single bonds are also represented also represented by Lewis dot.by Lewis dot.

Try bonding on Try bonding on your worksheet.your worksheet.