Atomic Theory and Structure

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Atomic Theory and Structure
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• The Theory of the Atom
• ___________, a Greek teacher in the 4th Century
  B.C., first suggested the idea of the atom.
• All matter is composed of tiny, _________
  particles called _______
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Democritus
indivisible
atoms
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John Dalton

• In 1803, ____________ studied experiments and
  concluded that the
  properties of matter could be explained in terms
  of _____.

atoms
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• Daltons _____________ had 4 points
• Each ________ is composed of extremely small
  particles called atoms (which are indivisible).
• All atoms of a given element are _______, but
  they differ from those of any other element.

Atomic Theory
element
identical
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• 3. Atoms are neither ________ nor ________ in any
  chemical reaction.
• 4. A given _________ always has the same relative
  numbers and kinds of atoms.

Atomic Theory Continued
created
destroyed
compound
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Daltons Model of the Atom
He believed the atom was a solid
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The Atom

• Is composed of an __________ is an atom.
• The atom is made up of three ___________
  particles ________,
• ___________ and __________

ELEMENT
SUBATOMIC
PROTONS
NUETRONS
ELECTRONS
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• Michael Faraday
• 1893
• Atoms contain particles that have an __________
  charge

electrical
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Electron

• Discovered in 1897 by __________
• Has a _________ charge

JJ Thomson
negative
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Thomson also thought in addition to the
negatively charged electrons, there must be
something with a __________ charge because the
overall charge of the atom is ___________
positive
neutral
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Plum Pudding Model
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Ernest Rutherford

• Performed Gold Foil Experiment in ______.
• He shot _______ particles (very small, dense,
  fast and positively charged particles) at a thin
  layer of gold foil.

1909
alpha
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Gold foil
Alpha particles source
Detector screen
Alpha particles
Because of Thomsons Atom
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But, what he found was this
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Most of the alpha particles went straight through
but a tiny amount were deflected In the atom
there was something dense enough to deflect the
alpha particles ________ Like this
nucleus
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Importance of Rutherfords Experiment

• 1. Showed most of the atom is made up of empty
  __________
• 2. Proved the atom had a small, dense area in
  its center known now as the _____________
• 3. The nucleus has a _________ charge (must have
  __________ in it)

space
nucleus
positive
protons
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Rutherfords Atom
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• Other important discoveries

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Neutron

• Discovered in 1932 by ____________
• Has no charge (i.e. It is ______)

James Chadwick
neutral
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Proton

• Discovered in ______ by E. Goldstein
• Has a ________ charge

1886
positive
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Bohr Model
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• Modern Atomic Structure
• The atom is made up of 2 parts/sections
• (1) The _________ --- (in the center of the
  atom contains protons and neutrons)
• (2) The _____________ --- (surrounds the
  nucleus)

nucleus
electron cloud
Nucleus (protons and neutrons)
Electrons cloud (electrons)
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The Atom

• The smallest particle of an ________ is an atom.
• The atom is made up of three _________
  particles _______, _________, and _______

element
subatomic
protons
neutrons
electrons
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Particle Charge Location Mass (g) Mass (amu)
Proton (P ) Positive Nucleus 1.673 x 10 1
Neutron (N) Neutral (No charge) Nucleus 1.675 X 10 1
Electron (E ) Negative Around Nucleus 9.109 x 10 1 1837 (0)
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-24
-28
-
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Protons
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Overall Charge

• The overall charge of an atom is ____(neutral)
• So, the number of protons must _______ the number
  of electrons
• So, the atomic number also tells us the number of
  _______________in an atom

0
equal
electrons
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Mass Number

• The mass of an atom
• Measured in ________
• Equal to the total number of __________ and
  __________

AMUs
protons
neutrons
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How to determine..

• 1) The number of protons Look at ______________
• 2) The number of electrons Look at
  ______________(number of protons number of
  electrons)
• 3) The number of neutrons ___________ atomic
  number

atomic number
atomic number
Mass number
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Practice Problems

• 1) Find the of e-, p and n0 for sodium. (mass
  23)
• 2) Find the of e-, p and n0 for uranium.
  (mass 238)
• 3) What is the atomic and mass for the
  following atom?
• e- 15 n0 16

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Ions

• When an atom loses or gains one or more ________,
  it acquires a net electrical charge and is called
  an ____.
• 2 types of ions
• 1) Anion
• 2) Cation

electrons
ion
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Anions and Cations
Anion

• ____________ An ion that has more electrons
  than protons has a ___________ charge.
  (Gained Electrons)
• ____________An ion that has fewer electrons that
  protons has a _____________ charge.
• (Lost Electrons)

negative
Cation
positive
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Determining the Charge of an Ion

• of protons - of electrons

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Ion Notation
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Practice Problems

• 1) A neutral magnesium atom (atomic number 12)
  has 12 protons and 12 electrons. If the atom
  loses 2 electrons, what is the charge of the
  resulting ion?
• 2) How many electrons would be found in the ion
  O2-?
• 3) If an ion has 28 protons and 26 electrons,
  what is its charge? What is its symbol
  (including charge)?

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Isotopes

• An isotope refers to atoms that have the same
  of ______, but they have a different of
  _______.
• Because of this, they have different ____ s (or
  simply, different ______.)

protons
neutrons
mass
masses
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• Exm (1) Carbon-12 Carbon-13
• (2) Chlorine-35 Chlorine-37
• (The shown after the name is the mass .)
• For each example, the elements have identical
  ______ s, but different _____ s

atomic
mass
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Isotopes cont

• In nature, elements are found as a
  _______________ of all their isotopes
• The isotopes are found in the same
  __________________

mixture
percentage
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More Practice Problems

• 1) Find the e-, p and n0 for Xe-131.
• 2) Find the e-, p and n0 for Cu
• 3) Write a shorthand way to represent the
  following isotope
• e- 1 n0 0 p 1

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Atomic Mass

• The atomic masses listed in the Periodic Table
  are a _____________ of all the isotopes of the
  element.

weighted average
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Practice Problems

• (1) Mrs. Smiths geometry semester grades are
  calculated using a weighted average of three
  category scores
• Tests/Quizzes 30 of your grade
• Homework/Participation60 of your grade
• Semester Exam 10 of your grade
• If a student had the following scores, what would
  they receive for the semester?
• Tests/Quizzes 80 (B-)
• Homework/Participation 60 (D-)
• Semester Exam65 (D)

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• Step (1) Multiply each score by the that it
  is weighted.
• Step (2) Add these products up, and that is the
  weighted average!
• A normal average would be calculated by simply
  adding the raw scores together and dividing by 3
• 80 60 65 205 3 68.3 D

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• (2) In chemistry, chlorine has 2 isotopes
• Cl-35 (75.8 abundance)
• Cl-37 (24.23 abundance)
• What is the weighted average atomic mass of
  chlorine?
• (3) Oxygen has 3 isotopes
• O-16 (99.76) O-17 (0.037)
• O-18 (0.2)
• Estimate oxygens average atomic mass.