Download Unit 2 Notes Atomic

video 2
.4
atomi
c th e o
ry
democritus (460-370bc)
Greek philosopher
!  His model of the atom:
! 
! 
! 
Coined the term “______” - atomos
john dalton (1808)
English scientist
!  His model of the atom:
! 
All elements composed of tiny particles called
ATOMS
!  Atoms of same element are ___________;
atoms of different elements are different
! 
Atoms are the __________ piece that any
substance can be broken down into
j.j. thomson (1897)
Discovered ___________ using a
cathode ray tube
!  His model of the atom:
! 
called “plum pudding” model
!  Atom is ____________ charged with negative
electrons embedded in it
! 
Dalton’s Model: Solid,
indestructible sphere
1
ernest rutherford (1911)
Discovered the _____________ with his
famous Gold Foil experiment
!  His model of the atom:
! 
Small, dense, __________ nucleus
!  Made of mostly _______________
! 
rutherford’s gold foil
experiment
The experiment:
Positively charged
alpha particles were
shot at a thin sheet
of gold foil.
!  The result:
! 
Most particles went
_______________.
!  A few were
_______________
! 
rutherford’s gold foil
experiment
! 
His Conclusion: (you must know this)
Atom is mostly _____________________
!  Atom has small, dense, __________ nucleus
! 
example
! 
When alpha particles are used to
bombard gold foil, most of the alpha
particles pass through undeflected. This
result indicates that most of the volume
of a gold atom is made of________.
1.
2.
!  3.
!  4.
! 
! 
a nucleus
neutrons
protons
unoccupied space
2
niels bohr (1913)
! 
wave mechanical model /
electron cloud model
His model of the atom:
Electrons travel around the nucleus in welldefined paths called ___________ (like
planets in a solar system).
!  Electrons in different orbits have different
amounts of _____________.
!  The further from the nucleus, the more
__________ an electron has.
! 
Present-day model of atom
!  Can not determine an
exact location of an
electron, only the
______________ of finding
an electron in a certain
place at a certain time.
!  ____________: region
where an electron is most
likely to be found
! 
3
video 2
.5
subat
omic
partic
les
subatomic particles
parts of the atom
atomic number
Equal to the number of __________
!  Every element has its own atomic number
!  Periodic table is arranged based on atomic
number
! 
Electron
Shells
________
1
mass number
The sum of the _________ and
____________(whole number)
!  Can be written as carbon-12
to find number of protons
! 
! 
Look up ___________on periodic table
! 
Ex. Lithium has ______ protons
to find number of electrons
Equal to the _______________in a neutral
atom
!  Ex. Lithium has ______ electrons
! 
to find number of neutrons
Protons + Neutrons = Mass Number
!  Neutrons = ________________________
!  Ex. Lithium has ____ neutrons (7-3 = 4)
! 
2
to find nuclear charge
! 
Equal to the _________________
! 
Ex. Lithium has a ______nuclear charge
example: fill in the table
ions
Ions: ____________ particles
!  Formed when atoms gain or lose _______
! 
cations
The atom loses electrons and becomes
_____________ charged
!  Ex. Na+
! 
Na Atom:
7p+
7e(neutral)
Na+ Ion:
7p+
6e(+1 charge)
3
anions
example
The atom gains electrons and becomes
_____________ charged
!  Ex. Cl! 
Cl Atom:
17p+
17e(neutral)
Cl- Ion:
17p+
18e(-1 charge)
4
video 2
.6
isotop
averag es and
e atom
ic
mass
complete chemical symbols
isotopes
! 
Elements that have the same atomic
number, but different __________
(different numbers of ______________)
common isotopes of hydrogen
Show the mass # and atomic # of
element
!  Isotopes will have the same ________ #,
but different __________ #’s
! 
1
example
example
! 
The chemical symbol of carbon-14
! 
Write the chemical symbol for oxygen-17:
! 
How many neutrons does it have?
! 
How many neutrons does it have?
calculating average atomic
mass
! 
example of a weighted average
Why is atomic mass not a whole number?
The atomic mass on the periodic table is a
__________________of the naturally
occurring ______________ of that element.
!  The atomic mass takes into account the
relative _____________ of the naturally
occurring isotopes of the element.
! 
2
example: determining avg
atomic mass
Boron-10
19.78%
10.013amu
Boron-11
80.22%
11.009amu
Step 1: Multiply the mass of each isotope by the percent
abundance IN DECIMAL FORM (move decimal 2 spots to
the LEFT)
example
Determine the average atomic mass:
Potassium-39
93.12% 38.964amu
Potassium-41
6.88%
40.962amu
! 
Step 2: Add the products from Step 1
3
video 2
.7
bohr d
iagram
bohr models
The greater the distance from the
nucleus…the greater the __________ of
the electrons in that shell (energy level)
!  The orbits are called principal energy
levels or ____________
! 
bohr models
! 
s
How do electrons orbit the nucleus?
! 
! 
In ___________________
Each principal energy level:
Is a __________ distance from the nucleus
!  Can hold a specific number of electrons
!  Has a definite amount of energy
! 
how many electrons can each
shell hold?
2n2
!  n = the ____________ number from the
periodic table or shell number
!  Ex. Max # of electrons in 1st shell is:
! 
! 
2 (1)2= ______ electrons
Increasing
energy
1
drawing bohr diagrams
example: bohr diagram of mg
Look up electron configuration on periodic
table (if it is an ion, add/subtract electrons
from outermost shell)
!  Draw a circle for the nucleus and notate
number of protons and neutrons in it.
!  Draw energy levels and notate number of
electrons in each shell.
! 
example: bohr diagram of mg+2
example: bohr diagram of ca+2
2
video 2
.8
ground
state
vs.
excite
d stat
e
and bri
gh t l i
spectr ne
a
example
! 
Possible excited states for Na:
ground state vs. excited
state
Ground state: when electrons occupy the
____________ available energy levels (the
configuration on the periodic table)
!  Excited state: electrons no longer occupy
the lowest energy levels. One or more
electrons ________ to a higher energy
level (different than electron configuration
on PT).
! 
how do you tell if the
configuration is ground or excited
state?
Add up total number of electrons in
configuration
!  Determine element
!  If it matches element’s configuration on
periodic table = ______________
!  If it doesn’t match = _____________
! 
1
example
! 
Identify the following electron
configuration as being ground state or
excited state: 2-6-1
bright line spectra
! 
Absorption:
Electrons ________ energy as they move to
__________ energy levels (excited state).
!  This excited state is temporary and
__________.
!  Electrons eventually fall back down to ground
state.
! 
2 + 6 + 1 = _______
!  9 electrons = _____________
!  Must be ______________ STATE
! 
bright line spectra
! 
Emission:
! 
Electrons are negatively charged and
therefore attracted to the positive nucleus, so
they eventually fall back to the ground state
and __________ energy in the form of
_____________.
bright line spectra
! 
Light:
! 
The color of the light is determined by the
amount of energy released by the electron
when it drops back down to the ground state
2
bright line spectra
! 
! 
! 
The different colors of light emitted produce a
pattern called a bright line spectrum.
Each element has a ____________ bright line
spectrum (like a fingerprint)
Bright line spectra can be used to ___________
unknown samples of elements
example
! 
What elements make up the unknown
sample?
3
video 2
.9
lewis
dot
diagram
s
lewis dot diagrams
Electron dot diagrams
!  Only show ____________ electrons
!  Valence shell: _____________ shell of an
atom that contains electrons
!  Valence electrons: electrons that occupy
the valence shell (last number in electron
configuration)
! 
steps to draw dot diagrams
Draw the element’s symbol
!  Locate valence electron number (last
number of electron configuration)
!  Draw dots around the element’s symbol to
represent the number of valence electrons
! 
example
! 
Draw the dot diagram for Carbon
C
1
example
! 
Draw the dot diagram for Sodium
Na
lewis dot diagrams: ions
Draw brackets around the element symbol
!  Write charge of ion outside of bracket in
top right corner of symbol
!  Positive ions: NO dots
!  Negative ions: 8 dots
! 
Na = 2-8-1
Na+ = 2-8
example
! 
Draw the dot diagram of K+
example
! 
Draw the dot diagram of S-2
2
example
! 
Draw the dot diagram of P and P-3
3