Chemistry I Chapter 3 Introduction to Atoms

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Chemistry I Chapter 3Introduction to Atoms
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How small is an atom?

• http//micro.magnet.fsu.edu/primer/java/scienceopt
  icsu/powersof10/

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Atoms
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Atoms vs. Hyle

• Atom - the smallest particle of an element. It
  can exist alone, or combined with other atoms.
• Atoms were first suggested by Democritus (Greek
  philosopher, 400B.C.).
• People that supported Democritus view were called
  Atomists.
• Aristotle(300B.C.) did not support the idea of
  atoms. He believed that all matter was a
  continuous substance called hyle. Hyle was
  composed of earth, air, fire and water.

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Democritus vs. Aristotle
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John Dalton.THE MAN!

• John Dalton-(English school teacher) first to
  explain the existence of atoms and disspelling
  Aristotles theory of matter.

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John Dalton

• Formulates Atomic Theory
• Each element is made up of tiny indivisible
  particles called atoms.
• The atoms of a given element are identical, atoms
  of different elements are different.
• Chemical compounds are formed when atoms come
  together, in simple whole number ratios.
• Chemical reactions involve the reorganization of
  the atoms combined, separated or rearranged.

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1903 J.J. THOMSON

• Discovers the electron, using his famous Cathode
  Ray Tube (CRT), which turns out to be a primitive
  TV or computer monitor.

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Discovery of the Electron
In 1897, J.J. Thomson used a cathode ray tube to
deduce the presence of a negatively charged
particle, the electron.
Cathode ray tubes pass electricity through a gas
that is contained at a very low pressure.
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CRT and TV
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1911 Ernest Rutherford

• Rutherford discovers the nucleus of an atom,
  using his famous gold foil experiment.

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Rutherfords Gold Foil Experiment
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Rutherfords Gold Foil Experiment
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Rutherfords Gold Foil Experiment

• Alpha (?) particles are helium nuclei
• Particles were fired at a thin sheet of gold
  foil
• Particle hits on the detecting screen (film) are
  recorded

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Rutherfords Gold Foil Experiment
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How big is an atom?
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Characteristics of sub-atomic particles

• Particle symbol charge location mass
• Proton p 1 nucleus 1 amu
• Neutron no 0 nucleus 1 amu
• Electron e- -1 orbital 1/1840 amu
• amu atomic mass unit, unit used to mass very
• small objects. (1 amu 1/12 the mass
  of a
• carbon-12
  nucleus)
• Orbital the 3-dimensional space around the
  nucleus of an atom, where electrons are found
  most of the time.

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Atomic Structure
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Atomic Models

• JJ Thomson model(Plum pudding model) electrons
  are scattered throughout the atom, like raisins
  in plum pudding.
• Rutherford Model-The atom has a central dense
  core, but is mostly empty space.
• Bohr Model(Planetary model)Electrons orbit the
  nucleus in circular paths, called energy levels
• Quantum Model (Modern, Shrodinger model)-
  Electrons move randomly in spaces called
  orbitals, around the nucleus.

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Thomsons Atomic Model
Thomson believed that the electrons were like
plums embedded in a positively charged pudding,
thus it was called the plum pudding model.
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Rutherfords Findings

• Most of the particles passed right through
• A few particles were deflected
• VERY FEW were greatly deflected

Like howitzer shells bouncing off of tissue
paper!
Conclusions

• The nucleus is small
• The nucleus is dense
• The nucleus is positively charged

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The Bohr Model of the Atom
I pictured electrons orbiting the nucleus much
like planets orbiting the sun.
But I was wrong! Theyre more like bees around a
hive.
Neils Bohr
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Quantum MechanicalModel of the Atom
Mathematical laws can identify the regions
outside of the nucleus where electrons are most
likely to be found.
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Important definitions about atoms

• atomic number number of protons in the nucleus
  of an atom. The number of protons determines the
  element of an atom.
• atomic mass number mass of the atom in amu, it
  includes the number of protons and neutrons.
• (electrons are not counted)
• Isotopes atoms of the same element, with a
  different number of neutrons in the nucleus.
  Isotopes of each element have the same atomic
  number, but different mass numbers.

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TAKS QUESTION
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Isotopes
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Boron isotopes
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(No Transcript)
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Find the number of protons, neutrons and
electrons in each

1. Carbon-14
2. Nitrogen-15
3. U-235
4. Hydrogen-3
5. Carbon-13
6. Helium-3
7. B-11
8. Cu-64

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Periodic Table Families
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List the Element Family

• Element Family Element Family
• Br Fe
• K U
• Sr Si
• Ce C
• Ar Cs

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• Orbital- the 3-d space around the nucleus of an
  atom where an electron is found most of the time.
  Each orbital can hold up to 2 electrons of
  opposite spin.

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Orbitals have different shapes

• Orbital shape
• s spherical
• p dumbbell
• d clover or
• dumbbell/donut
• f too complex

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Energy sublevels around an atom

• energy electron
• sublevels of orbitals capacity
• s 1 2
• p 3 6
• d 5 10
• f 7 14
• g 9 18
• orbitals exist, but not used most of the time.

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Aufbau Order- Energy levels orbital types
around the atom

• Aufbau order- Electrons fill orbitals closest to
  the nucleus first.
• 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p,6s,
  4f, 5d, 6p, 7s, 5f, 6d, 7p

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Orbital notation
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Electron configuration
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Valence Electrons/Lewis Dot Notation
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How to calculate average atomic mass
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Pre AP Chemistry Nuclear Equations

• Nuclear Reactions(transmutation reactions) are
  represented with Nuclear Equations.
• Transmutation reactions a reaction where one
  nucleus changes element.
• ( of protons)

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Nuclear equations

• See board

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Half-life the amount of time it takes for ½ of
a sample to react or decay.

• The half life of Ti-48 is 47 hrs. How much of a
  250 gram sample remains after 94 hrs?
• A 100gram sample of Cd-114 decays until only 12.5
  grams remain in a total of 41years. What is the
  half-life for this isotope?

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TAKS QUESTION
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Electron orbitals

• Orbital a 3-dimensional space around the
  nucleus which can hold up to 2 electrons, with
  opposite spin.
• electrons are found in their orbitals 99.9 of
  the time.
• Orbitals have different shapes s, p, d, f

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Orbitals have different shapes

• Orbital shape
• s spherical
• p dumbbell
• d clover or
• dumbbell/donut
• f too complex

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s-orbitals spheres
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p-orbitals dumbbell
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d-orbitals clover (double dumbbell) or
dumbbell/donut
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f-orbitals complex
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Energy sublevels around an atom

• energy electron
• sublevels of orbitals capacity
• s 1 2
• p 3 6
• d 5 10
• f 7 14
• g 9 18
• orbitals exist, but not used most of the time.

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Orbital Notation

• Aufbau Order
• (Nucleus)1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d,
  5p, 6s, 4f, 5d, 6p, 7s, 5f
• This is the order in which electrons
  fill!!!!!
• You must learn the order!! Dont worry there is
  always an easier way to memorize these things.
  For the Aufbau Order there are 2 ways With
  arrows or with the periodic table! Smartboard
  activate!

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Electron Configurations and the Periodic Table
Figure 8.7
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Orbital Notation

• Write the orbital notation for each atom
• Nitrogen, N(7 electrons)
• Sodium, Na(11 e-)
• Iron, Fe(__ e-)
• Antimony, Sb(__ e-)
• Gold, Au(__ e-)