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Differences Between Atoms
1) Atom – smallest particle of an element that retains its identity in a
Unit 2
chemical reaction
Atomic
2) Size of an atom
Structure
o 100,000,000 Cu atoms side by side would make a cm.
Spr.
3) Activity – Inference Tube.
2013
4) Elements are difference because of their subatomic particles.
o Protons – located in the nucleus, +1 charge, 1 amu (p+)
o Neutrons – located in the nucleus, 0 charge, 1 amu (n0)
o Electrons – Orbit the nucleus, -1 charge, 1/2000 amu (e-1)
5) Atomic mass unit (amu) – one-twelfth the mass of carbon-12 atom.
o Relative vs. Actual Masses
6) Atomic number (Z) – number of protons.
7) Protons must equal Electrons.
8) Mass number (A) – number of protons and neutrons.
9) Neutrons = Mass number (p+ & n0) – Atomic number (p+) A-Z
10) Use of the PT for determining the particles of atoms (what the boxes
mean)
11) Phet Lab: Build An atom
12) Isotopes – same number of protons, but a different number of
neutrons. Also different mass numbers.
 This makes them chemically alike, but leads to some more
interesting properties.
 Isotopic Notation 235/92 U or U-235
13) Atomic mass - weighted average of all of the naturally occurring
isotopes.
14) Use Table 4.3 pg 114 to calculate atomic mass on periodic table.
o Differentiate between average atomic mass, actual isotopic mass
and mass number of isotopes
15)
Lab – Isotope Lab
Model of the Atom
1) Our idea of the atom was mostly crafted between 1900 – 1932. WWI/II
2) Started with vague ideas and grew to more complex ideas.
3) Bohr Model for the Hydrogen Atom
o Electrons are found ONLY in fixed energy ranges in specific orbits
around the nucleus.
o Electrons can neither gain/lose energy inside the orbit, but can
move up or down to another orbit.
o The lowest energy orbit is closest to the nucleus.
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Each orbits corresponds to a specific amount of energy known
as an energy level.
Quanta – the amount of energy required to move between
energy levels. This is not uniform and like an uneven ladder.
Analyze and interpret the Reference Sheet Diagram.
Ground State – normal state of an atom. Lowest energy.
Excited State – happens when an electron gains a quanta or
more of energy and moves from the ground state to a higher
energy level. When it moves down to a lower energy level it
releases an amount of energy equal to the energy difference
(quanta) between the level as electromagnetic radiation. This
radiation is called a photon or a packet of “light”.
4) Brief review of a wave: amplitude, wavelength, frequency, crest, and
trough. Include units and symbols.
o Inverse relationship between wavelength and frequency and a
direct relationship between energy and frequency.
o c =λν E=hν
5) Review of electromagnetic spectrum.
o Relate the Bohr Model for the Hydrogen Atom to the
Electromagnetic Spectrum.
o Relate color, frequency, and wavelength of the light emitted to the
energy of the photon.
6) Lab – Flame test for atoms.
7) Duality of Electrons can act as both a particle and a wave under different
circumstances.
8) Classical mechanics good for motion larger than atoms while quantum
mechanics describes motion of subatomic particles. Explains duality
9) Heisenburg uncertainty principle – impossible to know the position and
velocity of a particle at the same time.
Electron Configurations
1) Accepted today is the Electron Cloud model which is based off of Calculus
and the probability of an electron to be located in a certain area. It is
better known as the Quantum Mechanical Model.
2) Quantum Numbers (p 304 in the AP book)
a) Principal Quantum number (n=1,2,3,4,5,6,7) - relates the size and
energy of the atomic orbital. (Energy Level)
b) Angular Momentum quantum number (l = n-1) – relates to the shape
of the atomic orbitals (Sublevel) Relates to s,p,d,f, etc.
c) Magnetic Quantum Number (ml = values between +/-l) – relates to
the orientation of the orbital.
d) Make table that relates n to l to sublevel designation to ml to Number
of orbiatls for the first 4 levels.
3) Electron configuration – arrangement of electrons into appropriate
orbitals.
4) Rules of assigning electrons
 Fill the lowest energy levels first. (Diagram)
 Each orbital can only have 2 electrons and they must have opposite
spins.
 If there is more than one level in an orbital each level must get one
electron before a gets two. Sharing.
5) Do electron configurations in box notations, shortened notation and noble
gas notation.
6) Include noble gas configurations.
7) Identify elements based on electron configurations
8) Must know all except exceptions.
9) Extend to Honors what exeptions are.
10) Explain and relate electron configurations of atoms to the Bohr and
electron cloud models.
Nuclear Radiation
1) Radiation – particles that are emitted by certain substance because they
are unstable and need to emit energy to become stable. Think isotopes
usually. Discovered by accident. Relate to Bohr/Electron Cloud.
2) Types of radiation
 Alpha particles – weakest of all particles (2 protons + 2 neutrons)
looks like a He nucleus without any electrons. Can be stopped by
paper, skin and very thin things. Mass of 4 amu, charge of +2.
Symbol.
 Beta particles – a high energy electron, formed when a neutron
breaks down. Medium strength and can be stopped by wood and
thicker items. Mass of 0 charge of -1. Symbol.
 Gamma ray – strongest of all radiation, no mass and no charge it is
an electromagnetic ray. Can be stopped by lead or thick concrete,
but even then not totally. Symbol.
 Diagram about types of radiation. And which way they
travel.
3) Nuclear Decay Activity
o Random even, independent of other energy influences
o Simple decay equations. Balance and Solve them for multiple
particles.
o Half-life – time required for one-half of the nuclei of a radioisotope
to decay away. Use of simple examples.
o Amount remaining = initial amount (0.5)^n n is number of half
lives
o n = t/T t is time elapsed and T is length of half-life
4) Half Life Acivity
5) Fission – splitting of the nucleus into smaller nuclei. (power plants)
6) Fusion – combining of nuclei to form a larger nucleus. (sun)
7) Compare radioactive decay with fission and fusion.