Chemistry 1201 Review/Preview
Chapter Eight Review Guide
Dr. Saundra McGuire
Basic Concepts of Chemical Bonding
Chemical Bonds, Lewis Symbols, and the Octet Rule
Chemical Bond – the strong attraction between two atoms or ions
Ionic Bond – the electrostatic attraction between ions of opposite
Covalent Bond – The bond formed due to sharing of electrons
Metallic bond – The bond found in metals, due to freely moving
electrons in the metal.
Lewis Symbols – show the symbol of an atom, along with the valence
electrons. (See Table 8.1 for the Lewis symbols of many of the elements.)
The Octet Rule states that atoms will gain, lose, or share electrons in order to
obtain eight electrons in their valence shell.
A. Energetics of Ionic Bond Formation
When forming ionic bonds from neutral atoms, and electrons must be
removed from the neutral metal atoms to form cations; electrons must be
added to the nonmetal atom to form anions; and the cations and anions must
be in close enough proximity for the electrostatic attraction to be felt.
Therefore, formation of an ionic bond involves different energies:
energy, electron affinity, and lattice energy.
The ionization energy is
positive (forming the cation requires energy input), the electron affinity is
generally negative (forming the anion generally releases energy), and the
formation of the lattice releases energy.
(See pages 305 – 306 and lecture
notes for a more complete discussion.)
B. Electron Configuration of Ions of the Representative Elements
The atoms of elements in groups 1A, 2A, and 3A form cations with charges
of +1, +2, and +3, respectively.
The atoms of elements in groups 5A, 6A,
and 7A form anions with charges of -3, -2, and -1, respectively.
C. The Transition Metals
The transition metals lose their s electrons first, and then d electrons.
Therefore the charges on transition metal ions are generally +1, +2, or +3,
depending on how many s and d electrons are lost.
What are they?
Lewis structures show the arrangement of electrons in a molecule.
electrons shown are the valence electrons of all of the atoms in the molecule.