Transcript The Structure of Matter

The Structure of Matter
Section 1 – Compounds and Molecules
Section 2 – Ionic and Covalent Bonding
Section 3 – Compound Names and Formulas
State Standards
• CLE.3203.1.6 – Distinguish between common ionic
and covalent compounds
• CLE.3202.1.7 – Construct chemical formulas for
common compounds
• CLE.3202.TE.4 – Describe the dynamic interplay
among science, technology, and engineering
within living, earth-space, and physical systems
1 – Compounds and Molecules
KEY QUESTIONS
• What holds a compound together?
• How can the structure of chemical compounds be
shown?
• What determines the properties of a compound?
Chemical Bonds
• Forces that hold atoms or ions together in a
compound are chemical bonds
– H and O form bonds when water is formed
Chemical Structure
• The way that atoms are bonded together to make
a compound results in chemical structure
• This structure can be shown by various models
– Example : Ball and Stick Model
Chemical Structure
• Some models show bond length and bond angles
– Ball and stick
• Other models show space occupied by compounds
– Space-filling model ( Figure 2 in Chapter 6 – page 178 )
– ETHANOL 
Bonds are like SPRINGS
• Bonds are flexible and act like springs
• Bonds can bend, stretch, compress, and twist
– Do this without breaking
• Temperature affects this motion ( Kinetic Theory )
How Structure Affects Properties
• Chemical structure determines properties
• Network structures form strong solids
– Quartz ( network of rigid Si-O-Si bonds )
– Have to break network to split up
• Some networks consist of bonded ions
– Salt ( NaCl formed from Na+ and Cl- ions )
– Group 1 elements form cations / Group 17 anions
• Some materials are made of separate structures
– Sugar is a group of single ( the same ) molecules
– Can pull out single molecules unlike with a network
Attractive Forces Vary
• Example : H2O
• Water is liquid at room
temp
• Sugar is solid at room
temp
• Indicates that water has
weaker attractive forces
Attractive Forces Vary
• Forces between molecules
• Example : H2O
• Water has higher boiling
point than H2S
• Indicates that water has
stronger attractive forces
1 – Compounds and Molecules
KEY QUESTIONS
• What holds a compound together?
• How can the structure of chemical compounds be
shown?
• What determines the properties of a compound?
2 – Ionic and Covalent Bonding
KEY QUESTIONS
• Why do atoms form bonds?
• Why do ionic bonds form?
• What do atoms joined by covalent bonds share?
• What gives metals their distinctive properties?
• How are polyatomic ions similar to other ions?
Why do Chemical Bonds Form?
• In general, atoms join
to form bonds so that
each atom may have a
stable electron
configuration
• They want a full level
of valence electrons!!
Ionic Bonding
• Formed from the attraction between ions
• Ions are formed by transfer of electrons
– Na and Cl form salt
• Ionic compounds form as networks
– Solids are the result
• Ionic compounds dissolved in
water conduct electricity
Covalent Bonds
• These are formed when
electrons are SHARED
• EXAMPLES : O2, Cl2, N2
• Atoms may share more
than one pair of
electrons
• Atoms do not always
EQUALLY SHARE
electrons
Metallic Bonds
• A type of covalent bond
• Occurs between metals
• Electrons move freely between
metal atoms
• Metals are flexible and conduct electricity well because
their atoms and electrons can move freely throughout
the packed structure
Polyatomic Ions
• Acts as a single unit in a compound, like ions that
consist of a single atom do ( like Cl, Na )
• Hydroxide ( OH - )
– NaOH
• Carbonate ( CO3 2- )
– CaCO3
• Ammonium Sulfate : (NH4)2SO4
+1 -2
Polyatomic Ions
• Some of these are named based on the number
of oxygen atoms in compound
• Nitrate vs Nitrite
– NO3- vs NO2-
• Chlorate vs. Chlorite
– ClO3- vs ClO2-
2 – Ionic and Covalent Bonding
KEY QUESTIONS
• Why do atoms form bonds?
• Why do ionic bonds form?
• What do atoms joined by covalent bonds share?
• What gives metals their distinctive properties?
• How are polyatomic ions similar to other ions?
3 – Compound Names & Formulas
KEY QUESTIONS
•How are ionic compounds named?
•What do the numerical prefixes used in naming
covalent compounds tell you?
•What does a compound’s empirical formula
indicate?
Naming Ionic Compounds
• Ionic compounds are named
based on the constituent ions
• Cations ( + ) are named based
on the element
– “calcium”
– “magnesium”
Naming Ionic Compounds
• Anions ( - ) are altered
names of elements
– “oxide”
– “chloride”
Put ‘Em Together
• sodium chloride ( NaCl )
• magnesium chloride ( MgCl2 )
• aluminum oxide ( Al2O3 )
Formula Unit
•
•
•
•
sodium chloride ( NaCl )
magnesium chloride ( MgCl2 )
aluminum oxide ( Al2O3 )
calcium fluoride ( CaF2 )
Wikepedia.org
Naming Ionic Compounds
• Charge ( + ) of many transition metals varies
– Fe may have 2+ or 3+
• Thus, some names show cation charge
– iron(III) oxide [common form ]
– iron(II) oxide
• Can also see charge in chemical formulas
– Fe2O3 [ Fe3+ since Oxygen is often O2- ]
– FeO [ both ions have a ‘2’ charge ]
Naming Covalent Compounds
• Numerical prefixes indicate
chemical formula when more
than atom is involved
• Examples:
– carbon dioxide ( CO2 )
– silicon dioxide ( SiO2 )
– boron tetrafluoride ( BF3 )
– Dinitrogen tetroxide ( N2O4 )
N2O4 via Wikepedia.org
Empirical Formulas
• Indicates the smallest whole-number ratio of
atoms in a compound
– Some are same as chemical formula
• Hydrogen Peroxide is exception:
• Chemical Formula – H2O2
• Empirical Formula – HO
• Formaldehyde, acetic acid, and glucose have same
empirical formula
Empirical Formula
• Molecular Formulas ( had Formula Unit for Ionics )
• Emprirical formula can be determined by analyzing
mass of each element in a compound
3 – Compound Names & Formulas
KEY QUESTIONS
•How are ionic compounds named?
•What do the numerical prefixes used in naming
covalent compounds tell you?
•What does a compound’s empirical formula
indicate?