Valence Electrons
Valence electrons are the electrons in the
highest occupied energy level of an element’s
atoms.
Electron dot structures are diagrams that
show valence electrons as dots.
Valence Electrons
The Octet Rule
The octet rule states that in forming
compounds, atoms tend to achieve the
electron configuration of a noble gas.
Formation of Cations
Formation of Cations
Formation of Anions
Formation of Anions
Formation of Ionic Compounds
Compounds composed of cations and anions
are called ionic compounds.
Formation of Ionic Compounds
A chemical formula shows the kinds and
numbers of atoms in the smallest
representative unit of a substance.
A formula unit is the lowest whole-number
ratio of ions in an ionic compound.
Molecules and Molecular Compounds
Atoms held together by sharing electrons are
joined by a covalent bond.
A molecule is a neutral group of atoms joined
together by covalent bonds.
A diatomic molecule is a molecule consisting
of two atoms of the same type.
Molecules and Molecular Compounds
A compound composed of molecules is called
a molecular compound.
Molecular Formulas
Single Covalent Bonds
Two atoms held together by sharing one pair
of electrons are joined by a single covalent
bond.
Single Covalent Bonds
A pair of valence electrons that is not shared
between atoms is called an unshared pair.
Single Covalent Bonds
Double and Triple Covalent Bonds
A bond that involves two shared pairs of
electrons is a double covalent bond.
A bond that involves three shared pairs of
electrons is a triple covalent bond.
Binary Ionic Compounds
A binary compound is composed of two
elements and can be either ionic or molecular.
To name any binary ionic compound, place the
cation name first, followed by the anion name.
SnF2 = tin(II) fluoride
MgO = magnesium oxide
SnS2 = tin(IV) sulfide
NaCl = sodium chloride
Fe2O3 = iron(III) oxide
Al2S3 = aluminum sulfide
Compounds with Polyatomic ions
To write formulas for compounds with
polyatomic ions, write the symbol for the
cation followed by the formula for the
polyatomic ion and balance the charges.
To name a compound containing a polyatomic
ion, state the cation first and then the anion
just as you did in naming binary ionic
compounds.
Naming Binary Molecular Compounds
A prefix in the name of a binary molecular
compound tells how many atoms of an
element are present in each molecule of the
compound.
Naming Binary Molecular Compounds
1. Confirm the compound is binary molecular
– a compound composed of two nonmetals.
2. Name the elements in the order listed in
the formula. Use prefixes to indicate the
number of each kind of atom.
3. The end of the name of the second element
is always changed to –ide.
Writing Formulas for Binary Molecular
Compounds
Use the prefixes in the name to tell you the
subscript of each element in the formula.
Then write the correct symbols for the two
elements with the appropriate subscripts.