What Are Compounds? What is a compound? What is an example of a
compound? What are chemical bonds? The attractive force that holds
atoms or ions together.
Slide 4
What Are Compounds? Chemical formula A combination of chemical
symbols and numbers to represent a substance. Shows the types and
numbers of atoms or ions making up the simplest unit of the
compound. Compounds will always be made of the same elements in the
same proportion. What are some examples of chemical formulas that
you know?
Slide 5
What Are Compounds? Chemical structure- Tells us the
arrangement of atoms in a substance. How the atoms in the compound
are arranged determines many of the compounds properties. Bond
length Give the average distance between the nuclei of two bonded
atoms. Bond angle The angle formed by two bonds to the same atom.
How the atoms are arranged in space.
Slide 6
Models of Compounds Models help us to see what a compounds
structure looks like. Some can give an idea of bond lengths and
angles. There are three models that are used to represent the
arrangement of compounds. Space filling Ball and stick Structural
formulas
Slide 7
Models of Compounds Space filling Shows the space occupied by
the atoms. In this type of model, it is hard to see the bond
lengths and angles.
Slide 8
Models of Compounds Ball and Stick This type of model helps us
in seeing a compounds structure. Shows how the atoms or ions are
arranged.
Slide 9
Models of Compounds Structural Formulas A formula that
indicates the location of the atoms, groups, or ions relative to
one another in a molecule. Indicates the number and location of
chemical bonds. Only shows the chemical symbols that represent the
atoms.
Slide 10
Lewis Dot Diagrams, For Compounds Draw the diagram for each
element listed in the compound. Draw the elements close together so
that where there are electrons missing, or single electrons, each
can line up and bond. Draw a line attaching the atoms together,
making sure that all of the atoms have 8 electrons. Exception for
Hydrogen and Helium.
Slide 11
How Does Structure Affect Properties? The strength of
attractions between molecules varies. Properties between molecules
can very differently from one another depending on the structure of
the molecules or compounds. Compounds can vary in properties
depending on the state at which the compound is at when at room
temperature.
Slide 12
How Does Structure Affect Properties? Attractions between water
molecules are called hydrogen bonds. What is a hydrogen bond? The
intermolecular forces occurring when a hydrogen atom that is bonded
to a highly electronegative atom of one molecule is attracted to
two unshared electrons of another molecule. Occur between oxygen of
one atom and the hydrogen of another atom.
Slide 13
How Does Structure Affect Properties? Hydrogen bonds Have a
higher boiling point than other compounds bonded to hydrogen. Bonds
are stronger connecting within each molecule than the bonds
connecting between the water molecules.
Slide 14
Section 2 Ionic and Covalent Bonding
Slide 15
What Holds Bonded Atoms Together? Atoms bond in different ways
to form many substances. The type of bonds formed between atoms
affect the substances properties. What bonds atoms? Electrons
Slide 16
What Holds Bonded Atoms Together? Atoms bond when their valence
electrons interact. Join to form bonds so that each atom has a
stable electron configuration. If the electron configuration is
stable, its electronic structure will be similar to what? A noble
gas
Slide 17
What Holds Bonded Atoms Together? When atoms bond, the
attraction between the nucleus of one atom and the electron of the
other atom pull the two atoms together. By pulling together, the
electron clouds overlap and form a bond. The bond will not break
apart unless there is enough energy added to break the bond.
Slide 18
What Holds Bonded Atoms Together? Bonds between atoms can bend
and stretch without breaking. Hold atoms tightly together, but can
move back and forth. Nuclei can change their distances between each
other. Bond lengths are given as averages due to this bending and
stretching. Think of the bonds as flexible springs.
Slide 19
What Holds Bonded Atoms Together? There are three different
kinds of bonds that describe the way atoms bond: Metallic bonds
Covalent bonds Ionic bonds
Slide 20
Metallic Bonds What are metallic bonds? A bond formed by the
attraction between positively charged metal ions and the electrons
around them. Nucleus of one atom is attracted by the electron cloud
of another metal atom. Due to the attraction, the atoms are closely
packed with each other, causing the outermost energy level to
overlap.
Slide 21
Metallic Bonds Overlapping of electron cloud causes the
electrons to be able to move from one atom to another. The movement
of the electrons help in explaining why metals can conduct
electricity well. Why are metals flexible? The atoms can slide past
each other without breaking bonds.
Slide 22
Ionic Bond What is an ionic bond? A bond formed by the
attraction between oppositely charged ions. Basically, a metal and
a nonmetal bonding together.
Slide 23
Ionic Bonds Ionic bonds are formed by the transfer of
electrons. One atom will give up or lose its electron or electrons
and the other atom will gain the electron or electrons. Each ion
that is formed will have a stable electron configuration. The
cation and anion formed, attract each other and form an ionic
bond.
Slide 24
Ionic Bonds When these compounds are melted or dissolved in
water, they conduct electricity. How do we get a current? What is
moving or going on to cause this current? Moving charges. Melting
or dissolving an ionic compound breaks the bonds and the ions break
apart. Ions are then floating in the solution moving charge
throughout.
Slide 25
Ionic Bonds Do ionic compounds have a high or low melting
point? High melting point because the ions are holding the
structure together tightly and will take a lot of energy to break
the bonds.
Slide 26
Naming Ionic Compounds How are ionic compounds formed? Between
cations and anions When naming the compounds, the cation is named
first, and has the name of the element.
Slide 27
Naming Ionic Compounds The names of the anions are named second
and are altered. The ending of the anion changes to ide.
Slide 28
Naming Ionic Compounds How we write chemical formulas for ionic
compounds is by going by the charge on the cation and anion. We
find the charges on the periodic table how? Charges are found by
looking at the periodic table and seeing how many valence electrons
each atom has. Metals all have a what kind a charge? Nonmetals all
have what type of charge?
Slide 29
Naming Ionic Compounds We cannot determine the charges of the
transition metals from the periodic table. Transition metals can
have multiple charges due to the electrons being able to rearrange
themselves into the orbitals differently. Allows them to form
different numbers of bonds.
Slide 30
Naming Ionic Compounds Transition metals use roman numerals to
state what charge is on the element.
Slide 31
Writing Formulas for Ionic Compounds When we have an ionic
compound, we can determine the charge by using the Criss-Cross
Method. This method can be used even when there is not a transition
metal. An exception that we will have to look for is if the
chemical formula has been simplified.
Slide 32
Covalent Bonds What are covalent bonds? A bond formed when
atoms share one or more pairs of electrons. These compounds are
made up of two or more nonmetals. Two or more elements on the right
side of the periodic table.
Slide 33
Covalent Bonds Most covalent compounds have low melting points
below 300C, but there are some exceptions. Most molecules remain
intact and do not conduct electricity when they are not molecules,
why? They are not comprised of charged ions when the bonds are
broken.
Slide 34
Covalent Bonds Atoms joined by covalent bonds share electrons.
They do not transfer between atoms because they both need to gain
electrons to form a full outermost energy shell.
Slide 35
Covalent Bonds Atoms can share more than one pair of electrons.
Single bond- when a pair of electrons bond, one line connecting two
atoms. Double bond- when 2 pairs of electrons bond, two lines
connecting two atoms. Triple bond- when 3 pairs of electrons bond,
three lines connect two atoms.
Slide 36
Covalent Bonds As we increase from a single to a triple bond,
we are increasing in energy. Why? The distance between the atoms is
shorter. Atoms are held more tightly. More energy is needed to
break the bonds. Single is easiest and triple is more
difficult.
Slide 37
Naming Covalent Compounds Prefixes are used to denote how many
of each atom are present in the chemical formula. The element that
is furthest on the right on the periodic table is named second and
has its ending changed to ide.
Slide 38
Polyatomic Ions Some compounds have both ionic and covalent
bonds. Polyatomic ions An ion made of two or more atoms. Groups of
covalently bonded atoms that have either lost or gained
electrons.
Slide 39
Polyatomic Ions These ions have a set formula that they are
known by. When writing polyatomic ions, parenthesis are put around
it to remind that it acts like a single ion. The charge for a
polyatomic ion is for the entire ion, not just one specific atom in
the ion.
Slide 40
Polyatomic Ions Some polyatomic anion names relate to their
oxygen content. Most of the polyatomic ions that contain oxygen
have the endings ite and ate. Does not tell how many oxygens are in
the polyatomic ion, but helps in learning the pattern. Polyatomic
with more oxygens has the ate ending. Example, Sulfate: SO 4
Polyatomic that has fewer oxygens has the ite ending. Example,
Sulfite: SO 3
Slide 41
Section 4 Organic and Biochemical Compounds
Slide 42
Organic Compounds What is an organic compound? A covalently
bonded compound that contains carbon, excluding carbonates and
oxides. These compounds always contain carbon and almost always
hydrogen. Oxygen, nitrogen, sulfur and phosphorous can be found in
organic compounds as well.
Slide 43
Organic Compounds Carbon atoms form four covalent bonds in
organic compounds. Why? Form four bonds because they have four
valence electrons. When a compound is made of only carbon and
hydrogen, we call this a hydrocarbon.
Slide 44
Organic Compounds Methane is the simplest hydrocarbon and it is
formed when living matter, like plants, decay. Organic compounds to
know: Methane CH 4 Ethane C 2 H 6 Propane C 3 H 8 Butane C 4 H 10
Carbon can form single, double and triple bonds, but it can never
have more than four bonds to an atom. Can never have more than 8
total electrons.
Slide 45
Organic compounds Alkanes are hydrocarbons that only form
single bonds. When the hydrocarbon chain has more than 3 carbons,
the hydrocarbon can rearrange itself in three different ways:
Branched, unbranched or rings. Alkanes follow a pattern when
writing chemical formulas, except for the ring structures. C n H
2n+2 Carbon chains can go onto having double and triple bonds and
have specific names.