7.1
Compounds, Atoms, and Ions
• The simplest form of matter is an element.
• The smallest particle of an element is an atom.
• Some elements like to combine, or bond, to form
compounds in fixed proportions.
VOCABULARY
bond
valence shell
valence electron
ion
• For example NaCl and H2O are compounds.
• Each compound has properties that are different than those of the
elements they are composed of.
• For an element, the tendency to bond or form an ion is determined by
the number of electrons in its outermost shell called the valence shell.
• Bohr diagrams focus on the valence electrons.
7.1
Compounds, Atoms, and Ions
• Atoms tend to acquire the same number of valence
electrons as their nearest noble gas. Noble gases
have complete valence shells.
VOCABULARY
bond
valence shell
valence electron
ion
• An atom and an ion of the same element have
completely different properties, such as size.
• For example the Na atom is larger than the Na+ ion.
7.2
Chemical Bonding
• A chemical bond is a force that holds atoms
together to form compounds.
• There are two general types of bonds: ionic and
covalent.
VOCABULARY
chemical bonds
ionic compounds
ionic bonding
covalent
molecular compounds
• Ionic bonds involve a transfer
of electrons between atoms.
Ionic bonding forms ionic
compounds.
• For example CaF2
• Covalent bonds involve a sharing of electrons
between atoms. The basic unit of a covalently
bonded compound is a molecule. Covalent bonds
form molecular compounds.
• For example O2
covalent bonding
molecule
diatomic molecules
phases
states
7.2
Chemical Bonding
• Ionic compounds separate into ions when
dissolved in water and can conduct electricity,
while covalent compounds do not separate into
ions, nor do they conduct electricity.
VOCABULARY
chemical bonds
ionic compounds
ionic bonding
covalent
molecular compounds
covalent bonding
molecule
diatomic molecules
phases
states
7.3
Ionic Compounds: Chemical Formulas
and Naming
• A chemical formula describes the proportions of the
component elements.
• The chemical formulas for ionic compounds can be
predicted by balancing ion charges.
• The fundamental rule for
determining the chemical
formula for any ionic compound
is that the total ion charge for
the compound is zero.
• The chemical names are derived from the ion names.
• For example: NaCl = sodium chloride
K2O = potassium oxide
• Ionic compounds can be divided into three types:
• binary ionic compounds
• ionic compounds with multivalent elements
• ionic compounds with polyatomic ions
VOCABULARY
chemical formula
ion charge balance
multivalent
polyatomic ions
7.4
Molecular Compounds: Chemical
Formulas and Naming
• Molecular compounds result when atoms of non-metals share
electrons to bond.
• The chemical formulas for molecular compounds are derived from
their chemical names (and vice versa) based on a prefix system.
• Charge balancing is not required for molecular compounds.
CHAPTER
7
Compounds, Ions, and Molecules
• Compounds result when elements
bond together in fixed proportions.
• Bohr diagrams can illustrate how ions form by focusing on the
atom’s electrons.
• Atoms tend to acquire the same number of valence electrons as
their nearest noble gas.
CHAPTER
7
Compounds, Ions, and Molecules
• A chemical bond (a force that holds atoms
together to form compounds) can involve
electron transfer or electron sharing.
• Ionic bonds involve a transfer of electrons
between atoms. Ionic bonding forms ionic
compounds.
• Covalent bonds involve a sharing of
electrons between atoms. Covalent bonds
form molecular compounds.
• Rules for writing chemical formulas and for
naming ionic compounds are based on ion
charge balances.
• Example: The chemical formula for sodium
oxide is Na2O.
CHAPTER
7
Compounds, Ions, and Molecules
• Rules for writing chemical formulas and for naming molecular
compounds are based on a prefix system. Ionic bonds involve a
transfer of electrons between atoms. Ionic bonding forms ionic
compounds.
• Molecular compounds result when atoms of non-metals bond by
sharing electrons.
CHAPTER
7
Compounds, Ions, and Molecules
Activity
• In chapter 6, we looked at chemical families (the columns) in the Periodic
Table.
• In pairs, examine columns 1, 2, 16, and 17. Determine how many electrons
each element would lose or gain to have the same number of electrons as
its nearest noble gas.
• Do you notice a pattern
within the chemical families?
• What generalizations can
you make about the families
and the ions they may form?
• Can you predict the ions
group 13 elements will form?
• Confirm your predictions using
the textbook (pages 172–173).
CHAPTER
7
Compounds, Ions, and Molecules
Key Ideas
• Compounds result when elements bond together in fixed
proportions.
• Bohr diagrams can illustrate how ions form.
• Bonding can involve electron transfer (ionic) or electron sharing
(covalent).
• Rules for writing chemical formulas and for naming ionic
compounds are based on ion charge balances.
• Rules for writing chemical formulas and for naming molecular
compounds are based on a prefix system.