Bonding
A chemical bond is a force that
holds atoms together.
Two Types of Bonds
1. Ionic Bond – the attraction
between two oppositely charged
ions.
An ionic bond is formed when
atoms gain or lose electrons.
Ionic bonds form compounds.
Ion – an atom or group of atoms that
has become electrically charged. It is a
charged particle.
When an atom loses an electron, it
loses a negative charge and becomes
a positive ion.
When an atom gains an electron, it
gains a negative charge and becomes
a negative ion.
Ionic bond
Atoms that gain electrons have
a negative valence. (charge)
Atoms that lose electrons have
a positive valence. (charge)
2. Covalent Bonding – A type
of bonding in which electrons
are shared.
When covalent bonding occurs,
molecules are formed.
Covalent Bond
Compound – two or more
elements chemically combined
by gaining, losing, or sharing
electrons.
Molecule – a particle made of 2
or more atoms covalently
bonded together.
Chemical formulas – a
shorthand way to represent a
compound. ( H2O)
In a chemical formula, the
element with the positive
charge is always written first.
Valence number – The number
of electrons an atom needs to
gain, lose, or share to become
stable.
(Gain electrons – negative
valence)
(Lose electrons – positive
valence.)
Subscript – the number that
shows how many atoms of an
element are in the compound.
How to Write Formulas
• 1. Write the symbol correctly for both
elements.
• 2. Write the valence number above each
symbol. Make sure you have a positive
first, and then a negative.
• 3. Criss-cross valences to make a
subscript.
• 4. NEVER write 1 as a subscript. (It is
understood to be 1 if there is no number.)
• 5. Reduce to lowest terms.
Examples
• Sodium Chloride
• Copper (I) Sulfide
Aluminum Oxide
Iron (III) Iodide
1. Calcium Sulfide
2. Copper (I)Iodide
3. Potassium Chloride 4. Iron(III) Bromide
5. Sodium Nitride
6. Antimony (V) Oxide
Practice Problems
• Aluminum Bromide
• Calcium Iodide
• Copper (I) Chloride
•
•
•
•
•
Hydrogen Oxide
Magnesium Nitride
Potassium Sulfide
Barium Fluoride
Lead Bromide
Binary Compound – a
compound composed of 2
elements.
Polyatomic Ion- a group of
positively or negatively charged
covalently bonded atoms.
Calcium Phosphate
Tin (IV) Chromate
Ammonium Oxide
Magnesium Sulfate
Naming compounds – change
the ending of the second
element to – “ide”.
(Do not change the names of
polyatomic ions.)
Check to see if Roman numeral
is needed.
Ex: NaCl - Sodium Chloride
Fe2O3 – Iron (III) Oxide
Examples
• Zn3N2
______________________
• K2SO3
______________________
• CuO
______________________
• Ba(C2H3O2)2 _____________________