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Chapter 3 – Atoms and the Periodic Table

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					 Chapter 3 –
Atoms and the
Periodic Table
3.1 Atomic
 Structure
      Atoms
Derived from the Greek
 word meaning “unable
 to divide”.
They are the building
 blocks of molecules.
Every element is
 made of tiny,
 unique particles
 that cannot be
 subdivided.
Atoms of the same
 element are exactly the
 same.
Atoms of different
 elements can join to
 form molecules.
Atoms are made of
protons, neutrons,
  and electrons.
   Nucleus
The center of an
atom; made up of
   protons and
    neutrons.
     Proton
A positively charged
subatomic particle in
  the nucleus of the
        atom
    Neutron
A neutral subatomic
   particle in the
nucleus of an atom.
   Electron
  A tiny negatively
 charged subatomic
   particle moving
around outside of an
        atom.
Atoms have no overall
      charge.
Even though atoms have
 charged protons and
 electrons. They have an
 equal number of each. So,
 they cancel each other out.
    Bohr’s Model
In 1913, Neils Bohr suggested
 that electrons moves about a
 set path about the nucleus.
The path defines
 the electron’s
 energy level.
 Energy Level
Any of the possible
   energies of an
 electron may have
     in an atom.
 Modern theory states
 that electrons behave
   more like waves.
In 1925, Bohr proposed a
 new model, that the
 electrons do not follow a set
 path.
 Although we cannot know how the
 electron travels around the nucleus
  we can know where it spends the
majority of its time (thus, we can know
     position but not trajectory).
The “probability” of finding an electron
 around a nucleus can be calculated.
 Relative probability is indicated by a
series of dots, indicating the “electron
                  cloud”.
Electrons are
   found in
orbitals within
energy levels.
      Orbital
A region in an atom
 where there is a
 high probability of
 finding electrons.
Electrons may
 occupy four
   different
   orbitals.
      s - orbital
- Simplest orbital.
- Can only have one
 orientation in space,
 because its shaped like a
 sphere.
- Its shape enables it to surround the
  nucleus.
- 90% electron probability/cloud
  for 1s orbital (notice higher
  probability toward the center)
- It can hold a maximum of 2
  electrons.
    p - orbital
-it is a dumbbell-
 shaped and can be
 oriented in 3
 different ways in
 space. (3-Dimensions)
    d - orbital
-a more complex
 orbital.
-There are a possible
 of 5 orientations.
-All orbitals are very
 different in shape, each
 can contain a maximum
 2 electrons.
-Can contains a total of
 10 electrons in all.
Four of the d orbital’s
  resemble two
  dumbbells in a clover
  shape. The last d
  orbital resembles a p
  orbital with a donut
  wrapped around the
  middle.
     f - orbital
-a more complex
 orbital.
-There are a possible
 of 7 orbitals.
-All orbitals are very
 different in shape, each
 can contain a
 maximum 2 electrons.
-Can contains a total of
 14 electrons in all.
Electrons usually
occupy the lowest
  energy levels
    available.
And within each
  energy level,
electrons occupy
orbitals with the
 lowest energy.
An s orbital has the lowest
 energy.
A p orbital has slightly
 more energy, followed by
 a d orbital.
An f orbital has the
 greatest energy.
 Every atom has
  one or more
valence electron.
Valence Electron
An electron in the
outermost energy
 level of an atom.
 3.2 A Guided
  Tour of the
Periodic Table.
  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.
    Period
A horizontal row
 elements in the
 periodic table.
 As you move across a
  row the # of protons
increases by 1. As does
   the # of electrons.
Elements in the
  same group
 have similar
   properties.
      Group
(family) – a vertical
 column of
 elements in the
 periodic table
Elements in the
same group have
  the same # of
     valence
    electrons.
These elements are
  not exactly alike,
they have a different
  # of protons and
      electrons.
 Some atoms
  form ions
Some atoms may
    under go
   ionization.
    Ionization
The process of adding
 electrons to or removing
 electrons from an atom
 or groups of atoms.
These are valence
 electrons.
         Ions
An atom or a group of
 atoms that has lost or
 gained 1 or more
 electrons and therefore
 has a net charge.
    Cation
An ion with a
positive charge
Example: Lithium atom
Lithium is so reactive, it
 reacts with air. It has 1
 electron in the outer level
 of the s orbital. This one
 electron makes very
 reactive.
Removing this electron
 forms a positive ion
 (Li +)

Li + is less reactive,

 because now its outer
 energy level is full.
    Anion
 An ion with a
negative charge.
Example: Fluorine atom
Fluorine is also very
 reactive; however it
 gains an electron to
 become less reactive.
It has 7 valence electrons
 and needs only 1 to
 complete its outer energy
 level.
Therefore, easily gaining 1
 electron & becoming a
 negative ion (F -).
 Atomic Structure of
      Atoms
All atoms have different
 structure and different
  properties; therefore,
   different structure.
Atomic Number
     (Z)
  The number of
   protons in the
nucleus of an atom.
Examples:
Helium (He) has 2
 protons
 Z=2
Cesium (Cs) has 55
 protons
 Z = 55
Mass Number (A)
Mass number equals
the # of protons and
neutrons in the
nucleus in the atom.
Ex: Fluorine (F)
 has 9 protons and
 10 neutrons, A =
 19 for fluorine.
Although atoms of the
 same element always
    have the same
 Atomic number, they
  can have a different
    mass numbers.
     Isotopes
Any atoms have the
 same # of protons,
 but a different # of
      neutrons.
Ex: Hydrogen has 3
     isotopes.
1. Protium – has 1
 proton in its nucleus.
 (A = 1) Most common
 form
2. Deuterium – has 1
 proton and 1 neutron
 in its nucleus, call
 heavy hydrogen.
 (A = 2)
3. Tritium – has 1
 proton and 2
 neutrons in its
 nucleus. (A = 3)
  Atomic numbers (Z)
and mass numbers (A)
 maybe included with
 the chemical symbol.
        A
        ZX
      Mass Number
235
 92   U
  Atomic Number
 Calculating the # of
 neutrons in an atom.
If you know the Atomic
 number and the Mass
 number, all you have
 to do is subtract.
    # of Neutrons
           =
   mass # – atomic #

(# of Neutrons = A – Z )
    Ex: For our
   Uranium - 235
 # of Neutrons = A – Z
# of Neutrons = 235 – 92
   # of Neutrons = 143
The mass of an atom.
The mass of a single atom
 is very small. A single
 Fluorine atom is one
 trillionth of one billionth
 of a gram.
Because it is very hard
 to work with atomic
 mass are expressed in
  atomic mass units
        (amu).
atomic mass unit
     (amu)
A quantity equal to
1/12 of the mass of
a Carbon-12 atom.
  average atomic
       mass
The weighted average
of the masses of all
naturally occurring
isotopes of an element.
 EX: If we look back at
       Hydrogen.
There are 3 isotopes. The
 average atomic mass 1.00794
 amu. This means there are
 more isotopes of Hydrogen-1,
 than Hydrogen-2 or Hydrogen-
 3.
3.3 Families of
   Elements
Elements are either
classified as Metals
   or Nonmetals.
      Metals
The elements that are
 good conductors for
 heat and electricity.
Most elements
 are metals.
Usually solids
and shiny.
  Nonmetals
The elements that
 are usually poor
conductors of heat
  and electricity.
Nonmetals, except
 Hydrogen, are found on
 the right side of the
 periodic table.
Can be solids, liquids, or
 gases.
Solids are dull and brittle.
 There are some
nonmetals that can
  conduct under
      certain
  circumstances.
Semiconductors
The intermediate
 conductors of heat and
 electricity.
Sometimes called
 metalloids.
 Metals can be
 classified even
  further into 4
different groups.
  Alkali Metals
Highly reactive
 metallic elements
 located in Group 1
 of the periodic table.
•Has 1 valence
 electron.
•Can be easily
 removed to form a +1
 ion.
•Highly reactive.
 Look on your
 Periodic table.
Lithium Sodium
Potassium Rubidium
Cesium    Francium
Since they are so reactive,
  these elements are not
   found in nature. They
    combine with other
     elements to form
        compounds.
 Alkaline Earth
    Metals
The reactive metallic
 elements located in
   Group 2 of the
   Periodic Table.
•They have 2 valence
 electrons.
•They are less reactive
 than alkali metals.
•May form an ion of a +2
 charge if both valence
 electrons are removed.
   Look at the
  Periodic Table
•Beryllium Magnesium
•Calcium    Strontium
•Barium     Radium
They are combine with
 other elements to form
 compounds.
Ex: Calcium Compounds
 – shells of sea life, coral
 reefs, limestone, or
 marble.
 Magnesium
 Compounds –
 speeds up the
processes of the
 human body.
Transition Metals
   The metallic
elements located in
groups 3 – 12 of the
   periodic table.
•Much less reactive than
 Alkali or Alkaline
 Metals.
•Can lose electrons to
 form + ions.
•Some metals can lose up
 to 4 electrons.
  All Metals are good
  heat and electrical
      conductors.
They can be stretched and
 shaped without breaking.
Mercury is the only
  metal that is a
  liquid at room
   temperature.
Technetium and
Promethium are
   synthetic
   elements.
•Man made elements
 that are radioactive.
•Technetium is used to
 help diagnose cancer
 and other medical
 problems.
•Promethium is used in
 ‘glow in the dark’ paint.
•Elements with atomic #
 greater than 92 are man
 made as well.
     Nonmetals
•Found on the right side
 of the periodic table.
•Some elements in
 groups13-16 and all in
 groups 17 & 18.
•May gain
 electrons to form
 – ions
•Carbon combines with
 other elements to form
 millions of carbon
 containing compounds.
•Carbon compounds are
 found in both living and
 nonliving things.
 Nonmetals and
there compounds
 are plentiful on
      Earth.
    Halogens
The highly reactive
 elements located
 in Group 17 of the
 periodic table.
•The valence shell is
 almost full; therefore,
 these elements easily
 accept an electron.
•Creating a (-) ion,
 anion.
•Fluorine
•Chlorine
•Bromine
•Iodine
•Astatine
Noble Gases
•The unreactive
gases located in
Group 18 of the
 Periodic Table.
•These elements exist
 only as single atoms,
 instead of molecules.
•All gases are inert,
 non-reactive.
•Outer level is full of
 electrons.
•They don’t form with
 other elemental
 atoms to form atoms.
Helium Neon
Argon Krypton
Xenon Radon
Semiconductors
•Elements classified as
 nonmetals, each one
 has some properties of
 metals.
•Known as ‘metalloids’
•They are able to conduct
 heat & electricity.
•Silicon most familiar,
 used for computers and
 other electronic devices.
•Boron     Silicon
•Germanium
•Arsenic
•Antimony
•Tellurium
 3.4 Using
  Moles to
Count Atoms.
 Counting Things
•One of the first things
 we do as child.
•When we count large
 #’s of small things, we
 use counting units.
The mole is useful
for counting small
     particles.
      Mole
The SI base unit that
describes the amount
   of a substance.
A mole is a collection
   of a very large
 number of particles.
602,213,670,000,
 000,000,000,000
    Avogadro’s
     Constant
•The # of particles in
 1 mol; equals 6.022
 x 1023 /mol.
Molar Mass
 The mass in
grams of 1 mol
of a substance.
   Ex: 1 mole of
Titanium-22 atoms
has a molar mass of
      47.87 g
•Think of it as
 47.87 grams per
 mole of Titanium.
•47.87 g/mol
Molar mass of an
element in grams
  is the same as
 average atomic
   mass in amu.
Find the molar mass for
the following elements:
1.Gold
2.Einsteinium
3.Gallium
4.Cesium
Find the molar mass for
the following elements:
1.Gold        196.97 g
2.Einsteinium 252.08 g
3.Gallium      69.72 g
4.Cesium      132.91 g
Conversion Factors
A ratio equal to one
 that expresses the
  same quantity in
     two ways.
 Can be anything:
1 ream of = 500 sheets
 paper      of paper
1 inch = 2.54 cm
10 km = 6.2 miles
  Converting
Amount (mol) to
   Mass (g)
•1st establish the amount
 of matter in moles from
 the problem.
•2 nd look up the element

 of the period table and
 find its molar mass in g
 for conversion factor
 Conversion factor will
          be:
Atomic mass(g)=1 mole
          or
1 mole=Atomic mass(g)
 Set up for factor
  label method.
Given
 info
 Set up for factor
  label method.
Given   atomic mass of
 info      element
 Set up for factor
  label method.
Given    atomic mass of
 info       element
        1mole of element
Ex: How many grams
in 23 moles of Silver?
23 mol
 of Ag
Conversion Factor
  1 mol of Ag
       =
107.8682 g of Ag
Ex: How many grams
in 23 moles of Silver?
23 mol 107.8682 g
 of Ag   of Ag
Ex: How many grams
in 23 moles of Silver?
23 mol 107.8682 g
 of Ag   of Ag
       1 mol of Ag
2480.96 g of Ag
- Multiply #’s above the
 horizontal line
- Units of moles of Ag
 will cancel leaving just
 grams of Ag.
 Ex: How many grams
in 2.8 moles of Radon?
2.8 mol
 of Rn
Conversion Factor
   1 mol of Rn
       =
222.0176 g of Rn
 Ex: How many grams
in 2.8 moles of Radon?
2.8 mol 222.0176 g
 of Rn   of Rn
 Ex: How many grams
in 2.8 moles of Radon?
2.8 mol 222.0176 g
 of Rn    of Rn
        1 mol of Rn
621.64928 g of Rn
Converting Mass (g)
 to Amount (mol)
   Set up is the same
 except we switch/flip
 the conversion factor
         ratio.
 Ex: Convert 729 g of
     Th to moles.
729 g
 of Th
Conversion Factor
  1 mol of Th
       =
232.0381 g of Th
 Ex: Convert 729 g of
     Th to moles.
729 g    1 mol of Th
 of Th
 Ex: Convert 729 g of
     Th to moles.
729 g    1 mol of Th
 of Th
         232.0381 g of
           Th
3.142 mol of Th
Ex: Convert 50 g of Sr
       to moles.
50 g
 of Sr
Conversion Factor
  1 mole of Sr
       =
  87.62 g of Sr
Ex: Convert 50 g of Sr
       to moles.
50 g      1 mol of Sr
 of Sr
Ex: Convert 50 g of Sr
       to moles.
50 g      1 mol of Sr
 of Sr
          87.62 g of Sr
0.571 mol of Sr

				
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