Download The structure of Matter

The structure of
Matter
Forming compounds
Compounds and Molecules
O A compound is made of two or more
elements that are chemically combined.
O The forces that hold atoms or ions together
in a compound are called chemical bonds.
O When a chemical reaction takes place,
bonds are broken or formed, and a new
substance with new properties is produced.
O Atoms are rearranged!
Compounds and Molecules
O A reaction between hydrogen gas and
oxygen gas causes bonds to form and water
to be produced.
Review…
O A mixture is composed of different
substances that haven’t chemically
combined
O A compound is composed of different
substances that have combined
Are the following mixtures or compounds??
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•
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Air
Carbon dioxide
Vegetable soup
MgO
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Pure water
Ocean water
Hydrogen peroxide
Chocolate milk
Chemical Structure
O The chemical formula of water tells how
many of which elements are bonded
together, but not the actual arrangement of
the atoms.
O A compound’s chemical structure shows
how the atoms are bonded to make the
compound.
Structure Determines Properties
O Compounds with network
structures are held together
with strong bonds.
O They tend to be solids with
high MP and BP.
Structure Determines Properties
O Compounds that form molecules
are less attracted to one another
so are not held together as well.
O They tend to be gases or
liquids/solids with low MP and BP.
Why do atoms bond?
O Atoms need to become stable…which means
that they must have 8 valence electrons
(also called a noble gas configuration).
O Depending on how many valence electrons
the atom is starting with, it will give away,
steal, or share electrons in order to obtain 8.
O Atoms will form either IONIC or COVALENT
bonds.
O The way that an atom bonds determines
many of its properties.
Ionic Bonding
O Elements in groups 1 + 2 tend
to lose electrons. (It’s easier to
lose a couple than to find 6 or
7…) They become positive
ions.
O Elements in groups 16 + 17
tend to gain electrons. They
become negative ions.
O Ionic bonds tend to form
between metals and
nonmetals.
Ionic Bonding
Properties of Ionic Compounds
O Because salt (sodium chloride,
NaCl) is a network of ions, there
is no molecule of salt.
O The simplest ratio is 1 Na: 1 Cl
because 1 Na+ will “cancel
out” 1 Cl- .
O Not every ionic compound has
a ratio of 1:1.
O Calcium fluoride must have a
ratio of 1 Ca ++ : 2 F-
Properties of Ionic Compounds
O Electric current is moving charges.
O Solid ionic compounds do not conduct
electricity because the charged ions
are locked in place.
O If you dissolve it in water or melt it,
the ionic compound will conduct
electric current because the ions are
free to move.
Properties of Ionic Compounds
Naming Ionic Compounds
O Ionic Compounds are formed by the strong
attractions between oppositely charged
particles (cations and anions).
O The name of these compounds consist of
the names of the ions that make up the
compounds.
O Write the name of the positive ion first, then
the name of the negative ion by changing
the ending to –ide. (Sodium chloride)
Naming Ionic Compounds
Practice….
O Name the following:
O Aluminum sulfide
O Al2S3
O BaCl2
O Barium chloride
O BaO
O Barium oxide
O BeS
O Beryllium sulfide
O Ca3N2
O Calcium nitride
O MgO
O Magnesium oxide
Interpreting Formulas
O The subscripts tell how many of each type of
atom is in the compound.
O The coefficient tells how many units of the
compound are present.
Interpreting Formulas
O Within a compound, ADD up the atoms.
O If there is a coefficient, MULTIPLY.
Practice…
O How many atoms?
O Answers
O Al2S3
O 2 Al, 3 S
O 2 BaCl2
O 2 Ba, 4 Cl
O 4 BaO
O 4 Ba, 4 O
O 3 CsNO3
O 3 Cs, 3 N, 9 O
O 3 Ca3N2
O 9 Ca, 6 N
O MgO
O 1 each of Mg and O
Writing Ionic Formulas
1. Write the symbol for the positive ion with
its charge.
2. Write the symbol for the negative ion with
its charge.
3. “Criss-cross” the numbers of the charges
so that they become the subscripts for the
formula.
Practice
O Write the formula:
O Answers:
O Aluminum phosphide
O Al+3 P-3 = AlP
O Sodium fluoride
O Na+1 F-1 = NaF
O Lithium phosphide
O Li+1 P-3 = Li3P
O Sodium Phosphide
O Na +1 P-3 = Na3P
O Aluminum sulfide
O Al+3 S-2 = Al2S3
O Barium bromide
O Ba+2 Br-1 = BaBr2
Covalent Bonding
O Atoms need 8 valence electrons to be stable.
O Sometimes electrons will be shared between
atoms rather than being transferred from one
atom to another.
O This is called a covalent bond (think “co” like
“cooperate”…they work together to be stable.)
O Covalent bonds tend to form between
nonmetals.
Covalent Bonding
Chlorine atoms have 7 valence electrons, but
will share a pair of electrons in order for each
to have 8.
Covalent Bonding
O Sometimes, atoms will share more than one
pair of atoms.
O This is called a double or triple bond.
Covalent Bonding - Nonpolar
O In the example of
iodine, both atoms
are the same size, so
the electrons are
shared equally
between the two
atoms.
O This is called a nonpolar bond.
Covalent Bonding - Polar
O Other times, the electrons are not shared equally
between the atoms involved in the covalent
bond.
O The electron may be more strongly attracted to
one of the atoms and spend more time revolving
around that nucleus instead of the other.
O This results in a positive and negative end for the
compound (the end with the electron most of the
time is negative…).
O This is called a polar bond.
Covalent Bonding - Polar
O In water, the
oxygen keeps the
electrons more
time than the
hydrogens do
which makes the
oxygen end
negative and the
hydrogen end
positive.
Naming Covalent Compounds
O For covalent
compounds, the
name uses
prefixes to tell
how many of
each atom are in
the compound.
Naming Covalent Compounds
O Examples:
O BF3
Boron trifluoride
(if there is 1 of the first
element…no prefix,
change ending to –ide)
O N2O4 Dinitrogen
tetroxide
Practice
O Name the compound
O Answers…
O CO
O Carbon monoxide
O O2F2
O Dioxygen difluoride
O SiO2
O Silicon dioxide
O N2O
O Dinitrogen
monoxide
Writing Covalent Formulas
O Use the given prefixes to determine how
many of each type of atom are present in
the compound.
O Examples:
O Boron tribromide
BBr3
O Dioxygen difluoride O2F2
Practice
O Write the name
O Answers:
O CCl4
O Carbon
O PoF6
O
O SiI4
O
O As2O5
O P4S3
O
O
tetrachloride
Polonium
hexafluoride
Silicone tetriodide
Diarsenic pentoxide
Tetraphosphorus
trisulfide
Organic Compounds
O Organic compounds are covalently bonded compounds
that contain carbon.
O Most also contain hydrogen, as well as oxygen,
nitrogen, sulfur, and phosphorus.
O Examples:
O Aspirin – acetylsalicylic acid – C9H8O4
O Sweeteners–sorbital C6H12O6 ,
asparatame C14H18N2O5
Organic Compounds Hydrocarbons
O Carbon usually forms 4 covalent bonds, has
4 valence electrons – needs 4 more.
O Compounds that contain only carbon and
hydrogen are called hydrocarbons.
O Two of the simplest hydrocarbons are
methane and ethane.
O Many hydrocarbons are used as fuels.
Organic Compounds Polymers
O Large molecules that are chains
made up of smaller molecules
(monomers)
O May be natural (rubber, wood,
cotton, wool, starch, protein, DNA)
or man-made (plastics, fibers)
Organic Compounds Polymers
O Structure determines properties.
O Some are more flexible than others, some
have “memory” and can return to their
original shape
Organic Compounds –
Biochemical
O Carbohydrates –
O Sugars and starches
O Provide energy for living things
O Made up of the monomer glucose which is
broken down during respiration
O Body stores extra glucose as glycogen
Organic Compounds Biochemical
O Proteins –
O Provide structure and function to
parts of cells
O Composed of monomers called
amino acids
O Each amino acid is composed of
an H, an amino group (-NH2), a
carboxyl group (-COOH), and a
side group (R group) around a
central carbon
O Include examples such as
hemoglobin, insulin, antigens,
albumin, muscle fibers, etc.
Organic Compounds –
Biochemical
O Proteins are long chains of amino acids.
O Millions of proteins can be made.
O When you eat foods that contain protein,
your digestive system breaks them down
into the AA. Then your cells use them to
build the proteins needed for you!
Organic Compounds Biochemical
O DNA (deoxyribonucleic acids)
O Made up of nucleotide
monomers – sugar,
phosphate, nitrogen base
(A,T,C,G)
O When connected, the
nucleotides form a spiral
staircase shape
O The sequence of the
nucleotides determines the
proteins that are made by the
cell
Inorganic Substances
O Do NOT contain carbon
O Properties make them useful for specific
purposes
O Copper is ductile and a good conductor, so is used
in wiring.
O Aluminum has a low density, yet is still strong so
can be used in making airplanes.
O Water is a good solvent so is used in washing
clothes.
O Argon will emit light when conducting electricity but
is inert, so it used in light bulbs.