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Chapter 3 – Atoms and the Periodic Table_1_

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Chapter 3 – Atoms and the Periodic Table_1_ Powered By Docstoc
					           Unit 6 – The Nature of Matter
             Chapter 18 – Atoms and the
                                     Periodic Table


Objectives:
Students will be able to:
1. Explain the atomic theory.
2. State the charge, mass, and location of each part of an
atom according to the modern model of the atom.
3. Compare and contrast Bohr’s model with the modern
model of the atom.
4. Relate the organization of the periodic table to the
arrangement of electrons within an atom.
5. Explain why some atoms gain or lose electrons to form
ions.
6. Determine how many protons, neutrons, and electrons
an isotope has, given its symbol, atomic number, and
mass number.

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7. Describe how the abundance of isotopes affects an
element’s average atomic mass.
8. Locate alkali metals, alkaline-earth metals, and
transition metals in the periodic table.
9. Locate semiconductors, halogens, and noble gases in
the periodic table.
10. Relate an element’s chemical properties to the
electron arrangement of its atoms.
11. Explain the relationship between a mole of a
substance and Avogadro’s constant. (EC)
12. Find the molar mass of an element by using the
periodic table. (EC)
13. Solve problems converting the amount of an element
in moles to its mass in grams, and vice versa. (EC)




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I. Atomic Structure
A. What are atoms?
         1. Atoms are building blocks of
                   molecules
                   a. every element is made of
                   tiny, unique particles called
                   atoms that cannot be
                   subdivided
                   b. atoms of the same element
                   are exactly alike
                   c. atoms of different elements
                   can join to form molecules



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                   d. an atom is the smallest part
                   of an element that still has the
                   element’s properties
B. What is in an atom?
         1. Proton, neutrons, electrons
                   a. nucleus – the center of an
                   atom; made up of protons and
                   neutrons
                   b. proton – a positively
                   charged subatomic particle in
                   the nucleus of an atom




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                   c. neutron – a neutral
                   subatomic particle in the
                   nucleus of an atom
                   d. electron – a tiny negatively
                   charged subatomic particle
                   moving around outside
                   the nucleus of an atom
                             1) electron cloud – the area
                                      outside the nucleus
                                      where electrons are found
         2. Atoms have no overall charge
                   a. atoms have the same
                             number of protons (+) and

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                             electrons (-)
                   b. ie – Helium
                             charge of two protons     +2
                             charge of two neutrons    0
                             charge of two electrons   -2
                             total charge of a He atom 0


C. How do the structures of atoms
differ?
         1. atomic number - equals the
                   number of protons and the
                   number of electrons



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                   a. ie – uranium – 92 protons
                             and 92 electrons
         2. Mass number - equals the
                   total number of protons and
                   neutrons in the nucleus of an
                   atom
                   a. ie – fluorine – 9 protons and
                   10 neutrons = mass number of
                   19
         3. Calculating the number of
                   neutrons in an atom
                   a.                 mass number
                             - atomic number

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                             number of neutrons
         4. Isotopes
                   a. any atoms having the same
                             number of protons, but
                             different numbers of
                             neutrons
         5. Mass of an atom
                   a. atomic mass unit (amu) – a
                             quantity equal to one-twelfth
                             of the mass of a
                             carbon-12 atom




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                   b. average atomic mass – the
                             weighted average of the
                             masses of all naturally
                             occurring isotopes of an
                             element


D. Models of the Atom
         1. Bohr’s model compares
                   electrons to planets
                   a. energy level – any of the
                             possible energies an
                             electron may have in an
                             atom

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                   b. electrons move around the
                             nucleus like the planets
                             move around the sun
         2. Modern theory
                   a. electrons behave more like
                             waves on a vibrating string
                   b. electrons move so fast that it is
                   almost impossible to know where
                   they are at any given moment.
                   However, scientists can predict an
                   area where they probably are
                   located. this is called an
                   electron cloud.



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                   c. Energy Levels
                             1) Energy Level 1 – 2 e-
                             2) Energy Level 2 – 8 e-
                             3) Energy Level 3 – 18 e-
                             4) Energy Level 4 – 32 e-
                             5) Energy Level 5 – 50 e-
         3. Electrons are found in orbitals
                   within energy levels
                   a. orbital – a region in an atom
                   where there is a high probability
                   of finding electrons




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                             1) s orbital – sphere shaped
                             - closest to the nucleus
                             – holds 2 electrons
                             2) p orbital – dumbbell-
                             shaped
                             – 3 different orientations
                             each holding 2 e- or 6 total
                             3) d orbital
                             – 5 different orientations
                                                      -
                             – each can hold 2 e 10 total
                   4) f orbital
                   – 7 different orientations
                   - each can hold 2 e- – 14 total

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                   b. s orbital has the lowest
                   energy and f orbital has the
                   highest energy level
                   c. electrons will be found in the
                   lowest energy level and then fill
                   higher levels
         4. Every atoms has one or more
         valence electrons
                   a. valence electron – an
                   electron in the outermost
                   energy level of an atom and
                   that determines the atom’s
                   chemical properties

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II. The Periodic Table
A. Periodic law – properties of
         elements tend to change in a
         regular pattern when elements are
         arranged in order of increasing
         atomic number, or number of
         protons in their atoms
B. Use the periodic table to
         determine electron arrangement
         1. period – a horizontal row of
                   elements in the periodic table
         2. the number of protons
                   increases by 1 as you go from

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                   left to right on the periodic table
                   – the number of electrons also
                   increases by 1
         3. Carbon has 6 electrons
         Energy level Orbital # of e-
                                      1               s   2
                                      2               s   2
                                      2               p   2
C. Elements in the same group have
         similar properties
                   a. group (family) - a vertical
                   column of elements in the
                   periodic table

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III. Families of Elements
A. How are elements classified?
         1. metals – the elements that are
                   good conductors of heat and
                   electricity
         2. nonmetals – the elements that
                   are usually poor conductors of
                   heat and electricity
         3. semiconductors (metalloids) –
                   the elements that are
                   intermediate conductors of heat
                   and electricity



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B. Metals
         1. alkali metals – the highly
                   reactive metallic elements
                   located in Group 1 of the
                   periodic table
                   a. one valence electron - highly
                             reactive
                   b. not found in nature as
                             elements, but combined with
                             other elements forming
                             compounds




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         2. alkaline-earth metal – the
                   reactive metallic elements
                   located in Group 2 of the
                   periodic table
                   a. 2 valence electrons – thus
                             they often react with other
                             elements
         3. transition metals – the
                   metallic elements located in
                   Groups 3-12 of the periodic
                   table
                   a. less reactive than the alkali
                             and alkaline-earth metals

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         4. synthetic elements
                   a. all elements with atomic
                             numbers greater than 92 –
                             very bottom of the table
C. Non-metals
         1. On the right side of the periodic
                   table and hydrogen
         2. Carbon is found in three
                   different forms and can also
                   form many compounds
         3. nonmetals and their
                   compounds are plentiful on
                   Earth

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         4. halogens – the highly reactive
                   elements located in Group 17
                   of the periodic table
         5. noble gases – the uncreative
                   gaseous elements located in
                   Group 18 of the periodic
                   table
                   a. full outer energy level thus
                             they don’t react with other
                             elements
         6. semiconductors/metalloids
                   a. classified as nonmetals
                   b. have some properties of

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                                      metals
                   c. conduct heat and electricity




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