MODELS OF THE ATOM

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MODELS OF THE ATOM

• CHM 130
• GCC

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Review - Rounding

• Round 399

Hopefully you said 400 not 4. What is wrong with
4???
The zeroes ARE important, they are place holders.
400 and 4 are NOT the same! If you had 400 in
the bank but they said you had only 4 youd be
pissed off! Round 2389 to 2 sig fig, now round
to 1 sig fig
Answer 2400 NOT 24 2000 NOT
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1. An element is made of tiny, indestructible
particles called atoms. (Not quite true why?)
5.1 DALTONS ATOMIC THEORY
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2. All atoms of an element are identical and have
the same properties. (Not quite true why?)
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3. Atoms of different elements combine to form
compounds.
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4. Compounds contain atoms in small whole number
ratios.e.g. Each H2O molecule consists of one O
and two H atoms, not ½ atoms or ¾ atoms.
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5. Atoms of 2 or more elements can combine to
form different compounds. E.g. C and O may form
CO or CO2
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5.2 Thomson cathode ray experiment
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Thompson Plum Pudding Model http//highered.mcgr
aw-hill.com/sites/0072512644/student_view0/chapter
2/animations_center.html

• Atom is charged
• e-s are distributed throughout atoms like
  raisins in plum pudding

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5.3 Rutherfords Scattering Experiment
http//www.mhhe.com/physsci/chemistry/animations/c
hang_2e/rutherfords_experiment.swf
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Explanation of Scattering
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Nuclear Model
1) The atom is mostly empty space with electrons
moving around. 2) Each atom has a small, dense
nucleus with the Protons Neutrons.
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Rutherfords model
If nucleus size of a small marble, then atom is
the size of Cardinals stadium!
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Subatomic Particles
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5.4 Atomic Notation
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ATOMIC NUMBER

• Every atom of an element has the same of
  protons
• The of protons defines an element
• Carbon atoms ALWAYS have 6 protons

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Mass number
Mass number protons neutrons So how
calculate neutrons?
neutrons mass - protons
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Isotopes
Isotopes of an element have the same atomic
number ( pro), but a different mass number (
neu). Ex carbon-12, carbon-13 and
carbon-14 How many protons do the above have?
Neutrons?
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6, 7, 8
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• Ex. 1 Write the atomic notation for
  potassium-40.
• How many neutrons are there?
• ______________

40 19 21
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Ex. 2 a. Write the atomic notation for
bromine-81. b. How many neutrons are
there? _________________
81 - 35 46
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16 8 8 8 17 8 9 8 18 8 10 8
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5.5 Atomic Mass

• Masses of atoms are so small that we define the
  atomic mass unit (amu)
• Mass of proton neutron ? 1 amu.
• Mass of electron is basically zero amu

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Atomic mass
Atomic Mass in the P. Table is the weighted
average of all atoms for that element in the
world, so that is why it is NOT a whole number.
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Natural isotopes of carbon carbon-12 (98.89)
carbon-13 (1.11)
The atomic mass reported for carbon (12.01 amu)
is closer to carbon-12 since it is most abundant
isotope for C. (There is a ton more C-12 than
C-13.)
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Example Use the Periodic Table to determine the
most abundant isotope a. lithium-6 or
lithium-7 b. chlorine-35 or chlorine-37
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5.6 Light has two components
Wavelength (?) is the distance between peaks
Frequency (?) is the number of wave cycles
per second. (like a beat)
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• As wavelength ?, the frequency ?, and the energy ?

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Which wave has higher energy? Lower frequency?
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Radiant Spectrum
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5.7 In 1900, Max Planck proposed the
controversial idea that energy was emitted in
small bundles called quanta.

• a particle of light energy is called a photon

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Ball loses potential energy continuously as it
rolls down a ramp.
Ball loses potential energy in quantized amounts
as it bounces down a stairway.
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5.8 Bohr Model 1913

• Neils Bohr proposed that electrons orbit around
  the nucleus, occupying orbits with distinct
  energy levels.
  Electrons are quantized!

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Bohr model of the atom

• The electrons orbit around the nucleus kinda like
  planets orbit around the sun but in 3D.
• These orbits are called energy levels or shells.
  
• Each orbit has a specific radius and energy, so a
  certain distance from the nucleus.

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Bohr Model
The orbit closest to the nucleus is lowest in
energy the energy increases with distance from
the nucleus. Proven by line spectra.
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When the light from a heated element passes
through a prism, a series of narrow lines is
seen.These lines are the emission line spectrum.
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Atomic Fingerprints
Each element produces a different emission line
spectrum, so its own unique color.
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Each element has its own energy levels that are
unique.
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• Bohr theory explains 3 lines in H2 spectra.
• Electrons gain energy from heat or electricity
  and jump to a higher energy level. These
  excited electrons ultimately lose energy and
  drop to lower energy levels, which causes light
  to be emitted.

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5.9 Each Energy Level Can Be Subdivided Into
Sublevels.

• Levels 1-7
• sublevels s, p, d, and f.

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Each Level Has n Sublevels1st level has One
Sublevel 1s2nd level has Two Sublevels 2s
2p3rd level - Three Sublevels 3s 3p 3d4th level
- Four Sublevels 4s 4p 4d 4fThis is depicted
on next slide.
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• Orbitals are regions in space where there is a
  high probability of finding an electron.
• One orbital can hold a maximum of 2 electrons.

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Each sublevel contains a specific number of
orbitals.
s has 1 orbital p has 3 d has 5 f has 7 Orbitals
are boxes on next slide
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5.10 Electron Configuration Shorthand
description of electrons by sublevel.

• Sublevels are filled in order of increasing
  energy.
• 1s lt 2s lt 2p lt 3s lt 3p lt 4s
• You will do configurations for the 1st 20
  elements.
• Note the 3d sublevel is higher in energy than the
  4s which is why we fill 4s first

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Writing electron configurations

• of electrons?
• Fill in sublevels to reach that
• Use superscript numbers to indicate number of
  e-'s in each sublevel.
• Ex C is 1s22s22p2 (cause 6 electrons)

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Practice writing e- configurations

• Na
• O
• Ca
• C

• 1s22s22p63s1
• 1s22s22p4
• 1s22s22p63s23p64s2
• 1s22s22p2

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• The Periodic Table actually is arranged by s, p,
  d, and f sublevels.

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5.11 S Orbitals
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P Orbitals
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Cool orbital pictureshttp//winter.group.shef.ac.
uk/orbitron/
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Ch. 5 Self Test p. 140

• Try 1-4, 6-7, 9, 12, 14-15, 17-18
• Answers in Appendix J
• Try to answer first, then check your answer!
• Also work the problems in the online NOTES and
  worksheets.