Basic Atomic Structure

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Atomic Structure

• Ch 4-5

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Early thoughts on matter.
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5th Cen. B.C. Greek philosophers Leucippus and
Democritus

• What would happen if you chopped up matter into
  ever smaller pieces?
• Indivisible atomos

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John Daltons Atomic Theory (1803)

• 1-Matter composed of atoms
• 2-Atoms of an element are identical.
• 3-Atoms cannot be created or destroyed.
• 4-Atoms combine in whole number ratios.
• 5-In chem rxns, atoms are rearranged.

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Daltons Atomic Theory ..Supports and explains
previous laws.

• Law of
• Conservation of mass

• Law of
• Definite proportions
• or composition
• Ex Water is always
• 11.11 H
• 88.89 O

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Sec. 4.2 Subatomic particle discovery
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J. J. Thomson discovers electron (1897)

• Experiments with
• Electricity through cathode ray tube

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J. J. Thomson discovers electron (e-)

• Observations conclusions
• Rays deflected by magnetic field
• electrically charged
• Light rays glow from cathode (-) to anode ()
• negatively charged
• Rays moved metal wheel
• have mass are particles

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Cathode Rays being deflected by magnetic field

• Cambridge Physics - Discovery of the Electron

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Rutherfords discovers nucleusby aiming
a-particles at gold (1911)Rutherford's gold
foil experiment
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Rutherfords Gold Foil Experiment

• Rutherford's Gold Experiment

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Rutherfords Conclusions 1

• Positive a-Particles were deflected slightly?
• center of atom is positively charged

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Rutherfords Conclusions 2

• Most a - Particles went straight through ?
• most of atom is empty space

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Rutherfords Conclusions 3

• 1/10,000 a bounce straight back
• atom has small nucleus 1/10,000 size of
  atom

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Everybody say Keyaw!!

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Anyone ever accuse you of having an empty head?

• ..Well, you are made of atoms
• and they are mostly empty space.

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Other sub-atomic explorers..

• Goldstein Wein (1898) protons
• Positively charged
• 2000 X larger mass than electrons
• Chadwick (1932) neutrons
• neutral charge
• about same size as protons

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Scientists publish their discoveries

• Scientists do research
• Scientists publish discoveries
• Peer review
• New research ideas
• The work of many scientists reveals a still
  incomplete story about the atom
• (true in all areas of research)

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Summary of atomic structure
Particle Location Charge Relative Mass(amu) Actual Mass
Electron (e-)
Proton (p)
Neutron (no)
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Summary of atomic structure
Particle Location Charge Relative Mass(amu) Actual Mass
Electron (e-) Orbitals around nucleus 1- 0 9.11 x 10 -28 g
Proton (p)
Neutron (no)
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Summary of atomic structure
Particle Location Charge Relative Mass(amu) Actual Mass
Electron (e-) Orbitals around nucleus 1- 0 9.11 x 10 -28 g
Proton (p) Nucleus 1 1 1.673 x 10-24 g
Neutron (no)
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Summary of atomic structure
Particle Location Charge Relative Mass(amu) Actual Mass
Electron (e-) Orbitals around nucleus 1- 0 9.11 x 10 -28 g
Proton (p) Nucleus 1 1 1.673 x 10-24 g
Neutron (no) Nucleus 0 1 1.675 x 10-24 g
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Sec. 5.1
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What walks down stairsAlone or in pairs?
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Light - energy that can act as a wave

• Speed wavelength x frequency
• C ? ?
• Difference between two waves above?

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A Continuous spectrum is a rainbow -

• Produced when white light goes through prism

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Continuous spectrum vs. bright line spectra for
H, He, C
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A continuous spectrum

• Has ALL colors
• Because it has
• ALL ?
• b/n 380-750 nm

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A bright line spectrum

• Has specific colors because it has specific ?
  of light
• one ? one color

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• Bet you wondering
• Whats this have
• to do with atoms?

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How studying light helps us understand atoms 1

• Max Planck (1900)
• Said energy flows in packets called quanta
  (quantum)
• Plancks eqn to find E of a quantum
• E h ?

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How studying light helps us understand atoms 2

• Photoelectric effect
• When light of specific ? shines on metal..
• electrons leave the metal as electricity

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How studying light helps us understand atoms 3

• Einstein explained Ph Ef
• e- in metal absorb light as particles not as
  waves
• Photon particle of light
• E of photon found by using Plancks eqn E h ?

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How studying light helps us understand atoms 4

• Each element has unique bright line spectrum
  (bls)
• Unique bls unique set of ? unique energies
• Each color in bls has a specific ? and E given
  by
• c ? ?
• E h ?

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How studying light helps us understand atoms 5

• What causes a bright line spectrum?

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So what are electrons doing in atoms?

• Sec. 5.2
• Neils Bohr suggests e- orbit nucleus as planets
  do the sun
• Not accepted now
• Still use his suggested energy values, not
  pathway
• deBroglie e- have wave-like properties

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So what are electrons doing in atoms?

• Heisenberg stated Uncertainty Principle
• Cannot know both location and velocity of e-
  simultaneously

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So what are electrons doing in atoms?

• Schrodinger
• treated e- as a wave, (deBroglie)
• e- energy limited to specific values (Bohr)
• formulated eqn. to determine the probable
  location or orbital of an e-
• Quantum mechanics mathematically describes
  behavior of subatomic particles

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Atomic orbitals

• Atomic orbitals

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Sec. 4.3 How atoms differ

• Molar mass
• Atomic number
• different for each element
• number of p
• neutral atoms p e-

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Mass number

• Sum of p and no
• not on PT
• Isotopes atoms of same element with a different
  mass number.

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Symbols used for isotopes

• 35 ? mass ? 34
• Cl ? symbol ? S
• 17 ? atomic ? 16
• Cl 35
  S 34
• chlorine 35
  sulfur - 34

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Isotopes of H
Isotope Symbol Mass Atomic Neutron



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Isotopes of H
Isotope Symbol Mass Atomic Neutron
Protium H - 1 1 1 0


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Isotopes of H
Isotope Symbol Mass Atomic Neutron
Protium H - 1 1 1 0
Deuterium H - 2 2 1 1

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Isotopes of H
Isotope Symbol Mass Atomic Neutron
Protium H - 1 1 1 0
Deuterium H - 2 2 1 1
Tritium H - 3 3 1 2
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You Practice Atomic Structure Worksheet Part B
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Series on PT energy level principal
quantum number

• 1
• 2
• 3
• 4
• 5
• 6

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Series on PT energy level principal
quantum number
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Orbital shapes
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Sublevel Blocks

• s1 s2 p1 p2 p3 p4 p5 p6
• 1
• 2
• 3 d1 - d10
• 4
• 5
• 6

f1 - f14
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Follow Aufbau to write electron configurations