Atomic Structure

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Atomic Structure

• Topic 1

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Objectives

• To understand how the model of the atom has
  changed
• To know the subatomic particles and all their
  properties
• To understand electrons and their energies
• To be able to distinguish between ground, excited
  state and ion configurations
• To distinguish between different types of matter

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Early Studies of Matter

• The model of the atom is the work of many
  scientists over a long period of time
• Greeks
• Fire, air, water, and earth
• Boyle 1600s
• Gold and silver are elemental

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Dalton 1700s

• Atom basic unit of matter
• cannonball
• Daltons Atomic Theory
• All elements are composed of indivisible atoms
• All atoms of a given element are identical
• Atoms of different elements are different
  (different masses)
• Compounds are formed by the combination of atoms
  of different elements
• Not all correct today but the groundwork

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Thomson Plum Pudding

• Electron
• Atom has some negative charged particle found
  within

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Rutherfords Gold Foil Experiment

• Nucleus of atom discovered
• Nuclear model
• Experiment
• Alpha particle shot at a piece of gold foil

Results Conclusion
Most particle went through
Some were deflected
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Rutherfords Gold Foil Experiment
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Bohr Model

• Planetary model
• Electrons in definite fixed orbits
• How we draw them

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Wave-Mechanical Model

• Most modern model of the atom
• Gives electrons properties of both particle and
  wave
• Electrons with distinct amounts of energy moving
  in orbitals
• Orbitals region in which electron is likely to
  be located

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Structure of the Atom

• Positive nucleus and negative electrons in
  regions called orbitals outside nucleus

Proton Neutron Electron
Charge
Mass
Location
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Atomic Number

• Atomic Number is the number of protons
• Atomic number protons
• Each element has its own atomic numberit
  identifies what element you have

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Complete Chart
Atomic Number 4
protons 32 80
Element symbol Xe
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Atom is neutral

• Neutral means equal amount of positive and equal
  amount of negative
• SOOO. WHAT 2 SUBATOMIC PARTICLES WILL BE EQUAL
  IN AN ATOM?
• Remember APE

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Mass Number

• Mass number is the mass of the nucleus (protons
  neutrons)
• Mass protons neutrons
• Mass - protons neutrons
• Notation C-12 126C

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Complete Chart
Element symbol Atomic number Mass number protons neutron
C 8
12 6
17 18
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Isotopes

• Isotopes are atoms of the same element that have
  different numbers of neutrons (giving them
  different mass numbers)
• Same protons (atomic numbers)
• Different neutrons (mass numbers)

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Atomic Masses

• Average masses of all the naturally occurring
  isotopes
• Weighted average

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Finding Atomic Mass Problems

• Carbon has 2 naturally occurring isotopes.
  98.89 of Cs are C-12 with a mass of 12 amu.
  The remaining 1.108 are C-13 with a mass of 13
  amu. What is the atomic mass of carbon?

Isotope Mass Abundance (decimal or percent key) Total for isotope


TOTAL Atomic Mass
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Sample Problem

• Element X three isotopes one that occurs 72.0
  with a mass of 84.9 amu, the second that occurs
  18.0 with a mass of 87.0 amu, and the last that
  occurs 10 with a mass of 89.1 amu. Find the
  average atomic mass of Element X.

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Solution
Isotope Mass Abundance Total for isotope



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Electrons, Electrons, Electrons

• Electrons surround the nucleus in regions called
  orbitals
• Electron Configurations for the atom are on the
  reference tables
• Tells how many electrons are in each energy level
• Last number in electron configuration is number
  of valence electrons (outermost electrons)

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Sample Questions

• Write the electron configuration of the following
  atoms
• Sodium
• Chlorine
• Fe
• Circle the valence electrons in the above atoms

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Energy of Electrons

• Each electron has its own distinct amount of
  energy that corresponds to the energy level that
  it occupies
• Higher the energy level the higher the electrons
  energy

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Ground vs. Excited State

• Electrons can gain or lose energy making them
  move to higher or lower energy levels
• Ground State electrons in their normal energy
  levels stable
• Found on the reference table
• Excited State electron gains energy and moves up
  to a higher energy level
• Start with configuration on table, keep same
  number electrons, but change the order

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Continued

• Ground ? Excited energy is __________
• Excited ? Ground energy is __________
• Calcium atoms electron configuration is
• Ground state
• Excited state

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Sample Problems
Atom Ground State Excited State
Cl
K
O
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Sample Problems

• Which shows an increase in energy?
• A - Electron that goes from the 2nd shell to the
  3rd shell
• B - Electron that goes from the 3rd shell to the
  2nd shell
• Which of the above A or B will produce a light
  spectrum?

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Ionic Radii
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Types of Matter

• Matter anything that has mass and takes up
  space (volume)
• Homogeneous uniform composition
• Can contain more than one type of particle, but
  the particles have to be evenly mixed
• Sugar water
• Heterogeneous varying composition
• Parts have there own chem and phys properties
• Chocolate chip cookie

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Matter
Pure Substance
Mixtures
All other heter. mixs
Compound
Element
Solutions
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Definitions

• Pure Substances composition is the same
  throughout
• Element substances that cannot be broken down
  or decomposed into simpler substances by chemical
  means

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• Compounds two or more elements that are
  chemically combined in definite proportions by
  mass
• Law of definite proportions types of atoms in a
  compound exist in a fixed ratio
• H2O2 vs. H2O
• H2O mass ratio of 18

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• Mixtures combinations of two or more pure
  substances that can be separated by physical
  means (not in fixed ratios)
• Heterogeneous mixtures
• Homogenous mixtures solutions