Chapter 19 Notes
Chemical Bonding
Chemical Formula:
 Tells what elements a compound contains
 Tells exact number of atoms of each element
 Ex: H20, NaCl, CO2
Subscript: “Written Below”
 Written after a symbol, tells how many atoms of
that element
 If NO subscript, then assume 1 atom
Ex: SiO2
Silicon=1 atom
Ex: H2SO4 Hydrogen = 2
Oxygen = 4
Oxygen=2 atoms
Sulfur = 1
Coefficient: Number placed in front of symbol or
formula in a chemical equation.
 Tells how many atoms or molecules
Ex: 3H2O Tells there are 3 molecules of water
Question: Why do atoms form compounds?
Answer: Atoms combine when compound formed is
more stable than separate atoms.
Chemically Stable: Atom is chemically stable when
its outer level is complete w/electrons.
*Noble Gases only elements w/full outer level
Chemical Bonding: Combining of atoms of elements
to form new substances.
 Outermost electrons determine if/how an atom
will bond.
 3 types: Ionic, Covalent, Metallic
Ionic Bonding: Chemical bonding that involves a
transfer of electrons.
 One atom gains electrons, one loses electrons
 Opposite charges hold ions together
 Between metals & nonmetals
Ex: NaF
Covalent Bonding:
Bonding in which electrons are
shared.
 Between non-metals and non-metals
 By sharing electrons, each atom fills its outer
energy level.
Ex: H2O
Metallic Bonding:
Bond formed by the atoms of
metals.
 Outer electrons form a common electron cloud
or “Sea of electrons”.
Predicting Types of Bonds
Metal + Metal
Metallic Bond
Metal + Non-metal
Ionic Bond
Non-metal + Non-metal
Covalent Bond