Download Chapter 20: Chemical Bonds

Chemical Bonds
Chapter 20
Sec. 1 - Combined Elements
• Elements make  compounds
• Properties of compounds are different
from elements
• Ex: Sodium Chloride, NaCl (table salt)
– Na: silver, metal, reacts violently w/ H2O
– Cl: poisonous greenish-yellow gas
Chemical Formulas
• H2O  2 atoms H
and 1 atom O
Atomic Stability
• Why do atoms form compounds?
• To be stable
• Why don’t noble gases form
compounds?
• Stable!  Full energy levels!!
• All atoms form compounds to get FULL
ENERGY LEVELS  stable
Atomic Stability
Atomic Stability
• 1st energy level full with 2 e• Other levels full with 8 e-
Stability is Reached
• NaCl is made from atoms losing or
gaining electrons
• H2O is different  elements share
electrons
• Both ways make a…
• Chemical Bond: force that holds atoms
together in a compound
Types of Bonds
Section 2
Ionic Bonds
• Atoms can lose or gain e- to make an ion
• Ion: a charged particle because it now
has either more or fewer e- than p+
• + charge: if fewer e- than p+
• - charge: if more e- than p+
Calcium Oxide - CaO
•
•
•
•
•
•
•
•
Calcium has 2 valence eLoses 2 e- and becomes an ion
Ca+2
Oxygen has 6 valence eGains 2 e- and becomes an ion
O-2
Calcium gives e- to Oxygen
Opposite charges ATTRACT!!
Ionic Bond – Metal and Nonmetal
• Def: the force of attraction between
opposite charges of the ions
• Ex: MgCl2 – zero net charge
• Smallest Particle = formula unit
Covalent Bond – 2 Nonmetals
• Def: attraction between atoms when
they share electrons
• Smallest particle = molecule
• H 2O
• CO2
• N2
Covalent Bonds
• Single Covalent Bond: 2 shared
electrons
• Multiple Bonds:
– Double (4 shared e-)
– Triple (6 shared e-)
Naming Compounds
Section 3
Naming Ionic Compounds
• Binary compound: has 2 elements
• Ionic compounds – name of ions makes
name of compound
• Positive Ions: name of element
– Na+ = Sodium ion
• Negative ions end in – ide
– Cl- = Chloride ion
Special Ions
Polyatomic Ions
Sec. 3 – Writing Formulas
•
Remember… compounds are
NEUTRAL!!
1. Write the (+) ion
2. Write the (-) ion
3. Balance charges: criss-cross method
•
Reduce to smallest whole #s
Write the Formula
•
•
•
•
•
Lithium Nitride
Lead(IV) Phosphide
Calcium Fluoride
Ammonium Phosphate
Magnesium Hydroxide
Naming Ionic Compounds
• Put the two ion names together!
• NaCl
– Na+ = Sodium ion
– Cl- = Chloride ion
– Sodium Chloride
Practice Naming
•
•
•
•
•
•
•
RbCl
Mg3N2
AlF3
CrCl3
Ca(OH)2
Na2CO3
NH4Cl
Naming Covalent Compounds
• No ions involved
• Same elements can make different
compounds: CO, CO2
• Naming: Use prefixes to tell how many
atoms of each element
• Second element ends in -ide
• Prefix mono is left out with the first
element
Prefixes
Practice Naming
•
•
•
•
•
N 4O 6
C 2O 5
PH3
Sulfur Hexafluoride
Dihydrogen Monoxide
Hydrates
• Def: has water chemically attached to
its ions
• CoCl2 • 6H2O
• Cobalt Chloride Hexahydrate
• CaSO4 • 2H2O
• Calcium Sulfate Dihydrate