Transcript Covalent Bond - Sharyland ISD

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
Compounds
 Naming Covalent
Compounds
 Chemical Formulas for
Covalent Compounds
 4.4 Organic and
Biochemical Compounds
 Organic Compounds
 Polymers
 Biochemical Compounds
Section 4.1 Compounds and Molecules
 Objectives:
 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 compound
 Chemical 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 Properties
 Compounds 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 molecules
 Salt and sugar are both white solids you can eat, but their structures are
very different.
Section 4.1 Summary
 Atoms 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 Objectives
 Explain 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 Bonds
 Metallic Bonds
 Covalent 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 Example
3. 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.
2.
They are often formed
between nonmetal
atoms and can be
solid, liquid, or gas.
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
Basic Unit
Compounds
Melting
Point
Conductor of
electricity
Example
Good
IONIC
COVALENT
ION
MOLECULE
HIGH
LOW
NaCl
Non
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 Report
 Atoms 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 Compounds
 Remember: 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 Compounds
 So….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 Chloride
Li3N
Lithium Nitride
Naming Ionic Compounds
 Now 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 124
 Notice that Roman Numerals are used.
 Roman Numerals represent the charge of the
transition metal.
Naming Metal Cations






So if you are given Fe2O3
What is Fe?
Iron
What is O?
Oxygen that changes to Oxide
So put them together and you have
but this is not it!
 What happened to the numbers?
Iron Oxide,
Naming Metal Cations
 Notice that is was Fe2O3
Charge of Oxygen
Charge of Iron
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
Writing Formulas for Ionic Compounds







By using the tables you can determine charges of ions.
How do we write chemical formulas?
Lets take aluminum fluoride
Aluminum from the table is Al3+
Fluoride from the table is F1So now you see Al3+ F1But this is not the formula
Writing formulas for Ionic Compounds
 Al3+ F1- What is the least common multiple of 3 and 1?
 The least common multiple of 3 and 1 is 3
 Your objective is to make the charges neutral
 So take Al3+ F1 Your formula is now AlF3
3 x -1 = -3
Writing formulas for Ionic Compounds
 Now try lithium oxide
 Lithium Li+1
Oxide O2 Together … Li+1 O2 The least common multiple is 2
 Li+1 O22x1=2
 Formula is now Li2O
Writing Formulas for Ionic Compounds
 How 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 Comounds
 Covalent 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 Compounds
 Remember that a covalent compound is a bond
when atoms share one or more pairs of electrons.
 Use Table 4-7 on page 126
 This 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 Compounds
 The prefix for 2 is Di
 Now how many oxygen are there?
 Correct… 4 so what is the prefix for 4?
 The prefix for 4 is tetra
 So given N2O4 using the prefixes we have
 Dinitrogen Tetroxide
Naming Covalent Compounds
 How about BF3?
 Boron Trifluoride
 Now As2O5
 Diarsenic pentoxide
Section 4.3 Review
 To name an ionic compound,
 An empirical formula tells the
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.
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 4.4
Organic and Biochemical Compounds
 Objectives:
 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 Hydrocarbon
 Alkanes 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 groups
 Alcohols 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 manmade:
 Natural polymers
 Man-made polymers
cotton
dermal fillers
epoxy
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 Compounds
 Biochemical 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 acids
 Amino 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 Report
 Alkanes have C-H bonds.
 Sugars and starches are
 Alkenes have C=C and C-H
carbohydrates that provide
energy.
 Amino acids bond to form
polymers called proteins.
 DNA is a polymer shaped like a
twisted ladder.
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.