MR. SURRETTE
VAN NUYS HIGH SCHOOL
CHAPTER 16: IONIC BONDING
CLASS NOTES
BONDING AND CHEMISTRY
Chemistry takes place when atoms combine or separate to make new products. All chemistry takes
place in the valence electrons of atoms.
MOLECULES AND IONS
Atoms that share valence electrons with other atoms become molecules. Atoms that completely gain or
lose valence electrons form ions.
BONDING THEORIES
Bonding theories examine valence electrons and predict the formation of molecules and ions. They
also explain the physical shapes of compounds and describe their physical and chemical properties.
LEWIS DOT STRUCTURES
Like other bonding theories, Lewis dot structure (LDS) diagrams predict the formation and placement
of chemical bonds.
LDS DIAGRAMS
LDS diagrams feature the valence electrons found within atomic elements 1 – 20 on the periodic table
(LDS diagrams do not track elements 21 or higher because they contain complicated transition
electrons).
ENTROPY
Over time, natural processes lose energy and revert to simpler, more stable states. This is called
entropy. Like water flowing downhill, electrons “fall” to their lowest energy levels because of entropy.
THE NOBLE GASES
Atoms with filled valence orbitals have no “open holes” waiting to be filled. These atoms can not hold
more electrons and rarely interact. These atoms are in the lowest energy states possible and are called
the noble gases.
NON-NOBLE GASES
The helium atom contains two valence electrons because of its small size. The other noble gases contain
eight valence electrons. All other elements conserve energy by copying the valence electron patterns of
the noble gases.
THE DUET/OCTET RULES
Hydrogen tries to become like helium and seeks two valence electrons. This is called the duet rule.
The other elements seek eight electrons. This is called the octet rule.
LDS DIAGRAMS
LDS diagrams allow two dots for hydrogen and helium. LDS diagrams allow eight dots for the other
elements.
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
LDS DIAGRAMS
LDS diagrams consist of atomic symbols surrounded by one to eight dots. Each dot represents a valence
electron. The first four dots are arranged evenly around the symbol. The second four dots are paired up
next to them.
Example 1. Provide the LDS diagram for phosphorus.
1A.
According to the periodic table, phosphorus is the fifth atom (counting left-to-right) in the third row.
This means it has five valence electrons:
Example 2. Provide the LDS diagram for silicon.
2A. Silicon has four valence electrons. Arranging these electrons around silicon gives:
IONIC COMPOUNDS
Ionic compounds form when electrons from metal atoms are completely transferred to nonmetal atoms.
IONIC STRUCTURE
The arrangement of ions in ionic compounds is highly ordered. Regular patterns appear where ions of
opposite charges surround one another.
IONIC CRYSTALS
Whenever ions of an ionic compound arrange themselves into a three-dimensional array, they form an
ionic crystal.
IONIC CRYSTAL EXAMPLE (NaCl)
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
IONIC BONDS
Metals and nonmetals follow the octet rule when they form ionic bonds. In particular, metal atoms lose
valence electrons and expose their outermost shell of eight core electrons. Nonmetal atoms receive
these electrons and complete their own existing set of valence electrons.
ELECTRON PAIRS
Valence electrons found on LDS diagrams pair up after the first four dots. It is common practice to
draw lines between paired electrons to represent filled orbitals. For example, the halogen gas fluorine
can be drawn two ways on a LDS diagram.
LDS DIAGRAMS FOR FLUORINE
LDS DIAGRAMS FOR IONS
Within LDS diagrams, nonmetal ions are surrounded by four lines. The metals attached to these
nonmetals have no lines around them.
LDS DIAGRAMS FOR IONS
When nonmetals gain electrons they become negative anions. When metals lose electrons they become
positive cations. In LDS diagrams, the metal cations are given plus signs. The nonmetal anions are
given minus signs and are placed in brackets (to represent the newly formed valence octets).
Example 3. Construct an LDS diagram for sodium chloride.
3a. Draw LDS diagrams for both sodium and chloride.
A.
3b. Show the transfer of electrons that forms sodium chloride.
A.
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
3c. Draw the LDS diagram for sodium chloride.
A.
LDS DIAGRAMS FOR IONS
LDS diagrams can also represent the transfer of two or more electrons between atoms.
Example 4. Construct an LDS diagram for magnesium oxide.
4a. Draw LDS diagrams for both magnesium and oxygen.
A.
4b. Show the transfer of electrons that forms magnesium oxide.
A.
4c. Draw the LDS diagram for magnesium oxide.
A.
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CHEMISTRY