Download 12.1 Atoms

12.1 Atomic
Structure
Subatomic Particles
• Subatomic particles are particles that are
inside the atom.
– proton
– neutron
– electron
Protons
•
•
•
•
positive charge
located in the nucleus (center of the atom)
accounts for the mass of an atom
always the same for atoms of the same element
Protons
• # of protons = atomic number
Check in:
• How many protons are in the atoms of the
following elements?
–O
– He
–C
– Al
• Do the number of protons in an atom ever
change?
Neutrons
• neutral charge
• located in the nucleus
• account for the mass of an atom
Electrons
• negative charge
• located in the electron cloud
• account for the volume of the atom
Comparing Particles
• protons and neutrons are MASSIVE
compared to electrons
– electrons mass is so small we tend to ignore it
• to determine the mass of an atom (mass
number)
mass # = protons + neutrons
Check-in:
• If an atom of oxygen has 8 protons and 7
neutrons, what is its mass?
• If an atom of chlorine has a mass number
of 36, how many neutrons does it have?
Atomic Forces
REVIEW:
• opposites attract
• likes repel
Protons and Electrons:
• opposite charges – attract
• attraction holds electrons onto the outside
of the atom
Atomic Forces
• Think: If like repel, then why are the
protons together in the nucleus?
• The strong force holds protons together in
the nucleus.
VIDEO: Just How Small is the
Atom???
• http://ed.ted.com/lessons/just-how-smallis-an-atom#watch
Varying Subatomic
Particles
• PROTONS NEVER CHANGE
FOR ATOMS OF THE SAME
ELEMENT!
• electrons and neutrons, however, CAN
change
Isotopes
• Isotopes are atoms of the
same element that have
different number of neutrons.
• If the number of neutrons
change, the mass of the
atom changes
• mass # = protons + neutrons
Ions
• ions are atoms that
have a charge
• atoms lose or gain
electrons to change
the overall charge
of the atom