Chapter 4

Chapter Preview 4.1 Compounds and

Molecules What Are Compounds? Models of Compounds How Does Structure

Affect Properties? 4.2 Ionic and Covalent

Bonding: What Holds Bonded

Atoms Together? Ionic Bonds Metallic Bonds Covalent Bonds Polyatomic Ions

4.3 Compound Names and Formulas Naming Ionic Compounds Writing Formulas for Ionic

CompoundsNaming Covalent

CompoundsChemical Formulas for

Covalent Compounds4.4 Organic and

Biochemical Compounds Organic Compounds Polymers Biochemical Compounds

Section 4.1 Compounds and MoleculesObjectives:

Distinguish between compounds and mixtures. Relate the chemical formula of a compound to the relative

numbers of atoms or ions present in the compound. Use models to visualize a compound’s chemical structure. Describe how the chemical structure of a compound affects its

properties.

What are Compounds? A compound is made up of two or more

elements.Ex : Table Salt made up of Na and CL

(NaCl)

Chemical bonds distinguish compounds from mixtures.Chemical bonds: the attractive force that holds atoms or ions together.

Compounds Chemical bonds distinguish compounds from

mixtures. Each substance in a mixture keeps its own properties.

A compound always has the same chemical formula. Chemical formula shows the types and numbers of atoms or ions making up the simples unit of the compound.

H20

Chemical structure shows the bonding within a compoundChemical structure: the arrangement of bonded

atoms or ions with a substance.

Two terms are used to specify the positions of atoms relative to one another in a compound.Bond length: the arrangement of bonded atoms or ions

within a substance.Bond angle: the angle formed by two bonds to the same

atom.

Models can represent physical events:Scientific model: is a representation of an object or

event that can be studied to understand the real object or event.

Three types of Models use to visualize Compounds

Some models give you an idea of bond lengths and angles. Types of Models:

Structural formulas: shows the structure of compounds.

Space-filling modes show the space occupied by atoms

The problem with this model is that it is harder to “see” bond lengths and angles.

Ball and stick model

This model makes it easy to see the bonds and the angles they form in a compound.

Structure Affects PropertiesCompounds with network structures are

strong solids.Some networks are made of bonded ions.

These strong attractions cause high melting and boiling points.

Good conductors of electricity.

Table Salt

Some compounds are made of moleculesSalt and sugar are both white solids you can eat, but their

structures are very different.

Section 4.1 SummaryAtoms or ions in compounds are joined by chemical bonds.A compound’s chemical formula shows which atoms or ions

it is made of.A model represents a compound’s structure visually.Substances with network structures are usually strong

solids with high melting and boiling points.

Section 4.2 ObjectivesExplain why atoms sometimes join to form bonds.Explain why some atoms transfer their valence electrons to

form ionic bonds, while other atoms share valence electrons to form covalent bonds.

Differentiate between ionic, covalent, and metallic bonds.Compare the properties of substances with different types

of bonds.

What Holds bonded Atoms Together? Atoms bond with other atoms when their

valence electrons interact.

Atoms with full outermost energy levels are non- reactive than atoms with only partially filled outermost energy levels.

Stable atom vs non stable atom:

Full Valence : Non Reactive

Partially Filled : More Reactive

Chemical Bonding In Action

Atoms want to join to form bonds so that they can fill the outermost energy levels.

Bonds: can bend and strtch without breaking

Bonds behave more like flexible springs than like sticks.

Three types of Bonds :Ionic BondsMetallic BondsCovalent Bonds

Ionic Bonds Ionic Bond – a bond formed by the attraction

between oppositely charged ions.

1. Atoms of metal elements form positive ions (cat- ion).

2. Atoms of non metal elements form negative ions (anion).

Ionic Bond Example3. Some atoms do not

share electrons:A. They transfer

electrons where one atom gains and one loses. This process is known as ionization.

B. Ions have filled valence energy level

C. They result in (+) and (–) ions.

D. Opposite charged ions attract and form ionic bonds ex:NaCl

Metallic Bonds Metallic Bond -

bond formed from attraction between positive charged metal ions and the electrons around them.

Metal ions are surrounded by what are known as delocalized electrons. Delocalized electrons are valence electrons from metal atoms. They move from one place to another and are not associated with a particular metal atom.

Covalent Bonds Covalent Bond –

bond formed when atoms share 1 or more pairs of valence electrons.

1. They are often formed between nonmetal atoms and can be solid, liquid, or gas.

2. They have a low melting point mostly below 300°C except silicon dioxide and any other compounds with network structures.

Atoms do not always share electrons equally: An unequal sharing

of valence electrons forms a polar covalent bond.

An equal sharing of valence electrons forms a non-polar covalent bond.

Ionic VS. Covalent Bonds

Types of Bonds in

CompoundsBasic Unit Melting

Point

Conductor of electricity Example

IONIC ION HIGHGood

NaCl

COVALENT MOLECULE LOWNon

conductor H20

Atoms do not always share electrons equally.Polyatomic ion: an ion

made of two or more atoms that are covalently bonded and that act like a single ion.

There are many polyatomic ions:

Section 4.2 Summary ReportAtoms bond when their

valence electrons interact.Cations and anions attract

each other to form ionic bonds.

When ionic compounds are melted or dissolved in water, moving ions can conduct electricity.

Atoms in metals are joined by metallic bonds.

Metals conduct electricity because electrons can move from atom to atom.

Covalent bonds form when atoms share electron pairs. Electrons may be shared equally or unequally.

Polyatomic ions are covalently bonded atoms that have either lost or gained electrons. Their behavior resembles that of simple ions.

Compound Names and Formulas

Section 4.3 Objectives:Name simple ionic and covalent compounds.Predicts the charge of a transition metal cation in an ionic

compounds.Write chemical formulas for simple ionic compounds.Distinguish a covalent compound’s empirical formula from

its molecular formula.

Naming Ionic CompoundsRemember: Ionic Bond = the attraction

between a positive and a negative ion (left side attracted to the right side of the periodic table).

Use Table 4-4 on page 123 and Table 4-5 on page 124 to show the charges for common cations and anions.

Remember: Anions (right side) change their name. Ex. Fluorine to Fluoride ion.

Naming Ionic CompoundsSo….if you are given CsBr, by looking at the

table you will see that Cs is Cesium and Br is Bromide therefore the compound’s name is… Cesium Bromide

Ok now CaCl2….Calcium ChlorideLi3NLithium Nitride

Naming Ionic CompoundsNow that you can see that all you have to do

is look at the table to name them, how about Metallic compounds?

Look at Table 4-6 page 124Notice that Roman Numerals are used.Roman Numerals represent the charge of the

transition metal.

Naming Metal CationsSo if you are given Fe2O3

What is Fe?IronWhat is O?Oxygen that changes to OxideSo put them together and you have

Iron Oxide, but this is not it!What happened to the numbers?

Naming Metal CationsNotice that is was Fe2O3

If you see that the charge for Iron is 3+

Then the name of the compound will now be

Iron (III) Oxide.

This only applies to Metal Cations in using Roman Numerals

Charge of IronCharge of Oxygen

Writing Formulas for Ionic CompoundsBy using the tables you can determine

charges of ions.How do we write chemical formulas?Lets take aluminum fluorideAluminum from the table is Al3+

Fluoride from the table is F1-

So now you see Al3+ F1-

But this is not the formula

Writing formulas for Ionic CompoundsAl3+ F1- What is the least common multiple of

3 and 1?The least common multiple of 3 and 1 is 3Your objective is to make the charges neutralSo take Al3+ F1-

Your formula is now AlF3

3 x -1 = -3

Writing formulas for Ionic CompoundsNow try lithium oxideLithium Li+1 Oxide O2-

Together … Li+1 O2-

The least common multiple is 2Li+1 O2-

Formula is now Li2O2 x 1 = 2

Writing Formulas for Ionic CompoundsHow about titanium (III) nitride?Here we have a metal cation so the charge of

titanium will be the roman numeral given.So…Titanium is Ti3+ and nitride is N3-

Together…Ti3+N3-

Notice that 3 is already the least common multiple so the formula will be TiN

Naming Covalent ComoundsCovalent compounds, like

SiO2 and CO2, are named using different rules than those used to name ionic compounds.

Numerical prefixes are used to name covalent compounds of two elements.

Naming Covalent CompoundsRemember that a covalent compound is a

bond when atoms share one or more pairs of electrons.

Use Table 4-7 on page 126This table will be used to determine the

prefix of the element when we name it.Given N2O4

How many Nitrogen atoms are there?Correct…2 so look at the table and what

is the prefix for 2?

Naming Covalent CompoundsThe prefix for 2 is DiNow how many oxygen are there?Correct… 4 so what is the prefix for 4?The prefix for 4 is tetraSo given N2O4 using the prefixes we haveDinitrogen Tetroxide

Naming Covalent CompoundsHow about BF3?Boron TrifluorideNow As2O5

Diarsenic pentoxide

Section 4.3 ReviewTo name an ionic

compound, first name the cation and then the anion.

If an element can form cations with different charges, the cation name must include the ion’s charge. The charge is written as a Roman Numeral in parentheses.

Prefixes are used to name covalent compounds made of two different elements.

An empirical formula tells the relative numbers of atoms of each element in a compound.

A molecular formula tells the actual numbers of atoms in one molecule of a compounds.

Covalent compounds have both empirical and molecular formulas.

Section 4.4Organic and Biochemical CompoundsObjectives:

Describe how carbon atoms bond covalently to form organic compounds.

Identify the names and structures of groups of simple organic compounds and polymers.

Identify what the polymers essential for life are made of.

Section 4.4 Organic and Biochemical Compounds In chemistry, the organic is used to describe certain

compounds.Organic compound: any covalently bonded compound that

contains carbon.Organic compounds contain carbon and, almost always,

hydrogen.Examples of Organic Compounds:

Acetylsalicylic acid, C9H8O4

Sorbitol: C6H14O4

Aspartame : C14H18N2O5

Carbon atoms form four covalent bonds in organic compounds.When a compound is made of only carbon and hydrogen

atoms it is called a hydrocarbon.The simples hydrocarbon is Methane CH4

Methane gas is formed when living matte, such as plants, decay, so it is often found in swamps and marshes.

Carbon atoms have four (4) valence electrons to use for bonding.

Types of HydrocarbonAlkanes are hydrocarbons

that have only single covalent bonds.

For example; Methane (CH4) :

Ehtane (C2H6) :

Propane: (C3H8) :

Arrangements of carbon atoms in alkanes can vary:

The carbon atoms in methane, ethane, propane and butane all lie up in a row this is called normal alkane.

Alkanes chains may be branched or unbranched, and they can even form rings.

Alkenes have double carbon-carbon bonds:Alkenes have at least one double covalent bond between

carbon atoms.This is shown by C=C.Alkenes are named like alkanes but with the –ane ending

replaced by –ene.

Alcohols have : -OH groupsAlcohols are organic compounds that are made of oxygen

as well as carbon and hydrogen.Alchohols have hydroxyl (-OH groups).Examples;

Alcohol methanol (CH3OH), is sometimes added to another alcohol ethanol, (CH3CH2OH), to make denatured alcohol.

Isopropanol, which is found in rubbing alcohol, has the chemical formula C3H8).

You may have noticed how the names of these three alcohols all end in –ol.

Polymers: a large organic molecule made of many smaller bonded units.

Some polymers are natural; others are man-made:Natural polymers

Man-made polymers

epoxy

cotton

dermal fillers

The elasticity of a polymer is determined by its structure:Polymer molecules are like

long, thin chains. In some cases the chains

are connected to each other, or cross-linked, the polymer becomes elastic.

Example: plastic bottles

BioChemical CompoundsBiochemical compound: any organic compound that has

an important role in living things.Carbohydrates : any organic compound that is made of

carbon, hydrogen, and oxygen and that provides nutrients to the cells of living things. Many carbohydrates are made of glucose.

The Power of Proteins:Proteins form important parts of your

body , like muscles, tendons, fingernails, and hair.

Proteins are polymer of amino acidsAmino acid: any one of 20 different naturally occurring

organic molecules that combine to form proteins.For example; Insulin is a protein that controls that use and

storage of glucose in your body.

DNA is a polymer with a complex structure:DNA determines your

entire genetic makeup.DNA is made of organic

molecules containing carbon, hydrogen, oxygen, nitrogen, and phosphorus.

Your body has may copies of your DNA.

DNA’s structure resembles a twisted ladder.

Section 4.4 Summary ReportAlkanes have C-H bonds.Alkenes have C=C and C-H

bonds.Alcohols have one or more

–OH groups.Polymers form when small

organic molecules bond to form long chains.

Biochemical compounds are polmers important to living things.

Sugars and starches are carbohydrates that provide energy.

Amino acids bond to form polymers called proteins.

DNA is a polymer shaped like a twisted ladder.