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?