Atoms, Molecules
& Ions
Page 22 # 1-10
Dr. S. M. Condren
Quantum Corral
http://www.almaden.ibm.com/vis/stm/corral.html
Dr. S. M. Condren
Scanning Tunneling Microscope
Dr. S. M. Condren
Developed in collaboration with the
Institute for Chemical Education and the
Magnetic Microscopy Center
University of Minnesota
http://www.physics.umn.edu/groups/mmc/
Dr. S. M. Condren
http://mrsec.wisc.edu/
http://mrsec.wisc.edu/
Atoms & Molecules
Atoms
• can exist alone or enter into chemical
combination
• the smallest indivisible particle of an
element
Molecules
• a combination of atoms that has its own
characteristic set of properties
Dr. S. M. Condren
Law of Constant Composition
A chemical compound always contains the
same elements in the same proportions by
mass.
Dr. S. M. Condren
Law of Multiple Proportions
• the same elements can be combined to form
different compounds by combining the
elements in different proportions
Dr. S. M. Condren
Structure of the Atom
Composed of:
• protons
• neutrons
• electrons
Dr. S. M. Condren
Structure of the Atom
Composed of:
• protons
• neutrons
• electrons
• protons
– found in nucleus
– relative charge of +1
– relative mass of 1.0073 amu
Dr. S. M. Condren
Structure of the Atom
Composed of:
• protons
• neutrons
• electrons
• neutrons
– found in nucleus
– neutral charge
– relative mass of 1.0087 amu
Dr. S. M. Condren
Structure of the Atom
Composed of:
• protons
• neutrons
• electrons
• electrons
– found in electron cloud
– relative charge of -1
– relative mass of 0.00055 amu
Dr. S. M. Condren
Size of Nucleus
Dr. S. M. Condren
Ions
• charged single atom
• charged cluster of atoms
Dr. S. M. Condren
Ions
• cations
– positive ions
• anions
– negative ions
• ionic compounds
– combination of cations and anions
– zero net charge
Dr. S. M. Condren
Atomic number, Z
• the number of protons in the nucleus
• the number of electrons in a neutral atom
• the integer on the periodic table for each
element
Dr. S. M. Condren
The identity of an element is determined by the
number of which particle?
protons, neutrons, electrons
Dr. S. M. Condren
Models of Sodium Chloride
NaCl “table salt”
Dr. S. M. Condren
How many atoms are in the formula Al2(SO4)3?
3, 5, 17
Dr. S. M. Condren
Ion Formation
Dr. S. M. Condren
Valance
Charge on Ions
• compounds have electrical neutrality
• metals form positive monatomic ions
• non-metals form negative monatomic ions
Dr. S. M. Condren
Valence of Metal Ions
Monatomic Ions
Group I
=> +1
Group 2
=> +2
Maximum positive valence
equals
Group A #
Dr. S. M. Condren
Valence of Non-Metal Ions
Monatomic Ions
Group 16
=> -2
Group 17
=> -1
Maximum negative valence
equals
(8 - Group A #)
Dr. S. M. Condren
Charges of Some Important Ions
Dr. S. M. Condren
Dr. S. M. Condren
Dr. S. M. Condren
A flow chart for naming binary compounds.
Copyright© by
Houghton Mifflin
26
Polyatomic Ions
• more than one atom joined together
• have negative charge except for NH4+ and
its relatives
• negative charges range from -1 to -4
Dr. S. M. Condren
Dr. S. M. Condren
How many moles of ions are there per
mole of Al2(SO4)3?
2, 3, 5
Dr. S. M. Condren
Names of Ionic Compounds
1. Name the metal first.
If the metal has more than one oxidation
state, the oxidation state is specified by
Roman numerals in parentheses.
2. Then name the non-metal,
changing the ending of the non-metal to
-ide.
Dr. S. M. Condren
Overall strategy for naming chemical compounds.
Copyright© by
Houghton Mifflin
31
Nomenclature
NaCl
sodium chloride
Fe2O3
iron(III) oxide
KI
potassium iodide
Mg3N2
magnesium nitride
Dr. S. M. Condren
Nomenclature
NH4NO3
ammonium nitrate
KClO4
potassium perchlorate
CaCO3
calcium carbonate
NaOH
sodium hydroxide
Dr. S. M. Condren