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Elements and the Periodic Table

VIEWS: 6 PAGES: 95

  • pg 1
									Elements and the Periodic Table

            Chapter 6
            (page 166)
            Essential question


• How does knowing the periodic table help
  scientist identify the physical and chemical
  characteristics of elements?
           Vocabulary Section 1
•   Trace amounts
•   Macronutrients
•   Trace elements
•   Periodic
•   Atomic radius
•   Electronegativity
•   Ionization energy
Are you made of star dust?

  The Big Bang produced
   hydrogen and helium
  and a tiny bit of lithium
Are you made of star dust?



   Other elements were
  created in the cores of
     exploding stars
• Scientist believe that all elements in the
  universe came from only four different
  elements
  – Hydrogen 75%
  – Helium 25%
  – Lithium (trace amounts)
  – Beryllium (trace amounts)
• Scientist believe that these elements came
  from nuclear reactions in distant stars
• It is believed that when smaller elements
  reacted, they produced larger elements like
  carbon and oxygen
• The universal reactions that created all these
  elements came from stars exploding, called
  supernova
• There are about 118 known elements and they
  all belong to one of three categories
  – Metals (conduct heat and electricity)
  – Nonmetals (poor conductors of heat and electricity)
  – Metalloids (properties of both metals and nonmetals)
• The human body is made up of mainly four
  elements

  – Hydrogen 63%
  – Oxygen 26%
  – Carbon 9%
  – Nitrogen 1.25%
99% of atoms in
a human body
come from only
4 elements
                    Trace Elements
• You are what you eat and the other elements that are
  found in your body are based on what is eaten and needed
  to survive
• Some of those trace elements include:
   –   Calcium
   –   Phosphorus
   –   Potassium
   –   Sulfur
   –   Sodium
   –   Chlorine
   –   Magnesium
   –   Iron
   –   iodine
                    Macronutrients
• Elements that your body needs a lot of to maintain good health.
• The macronutrients your body needs are:
   –   Hydrogen
   –   Sodium
   –   Potassium
   –   Calcium
   –   Magnesium
   –   Carbon
   –   Nitrogen
   –   Oxygen
   –   Phosphorus
   –   Sulfur
   –   chlorine
                              Essential elements




macronutrients: elements needed in large quantities by
your body.
trace elements: elements that are needed in very small
quantities to maintain optimum health.
• Macronutrients helps to regulate the body’s
  function as well as to repair damaged parts
• Protein, carbohydrates, DNA, and fats are
  needed for the body to live and survive and
  are made of hydrogen, carbon, nitrogen,
  oxygen, phosphorous and sulfur
                  Assignment

• Take a new sheet of paper and fold it into
  three sections
• Write your name, the title of the chapter
  and the number
• On the first section from the sheet of
  paper, please write six things that you
  learned from your notes so far that could
  appear on your test.
    History of the Periodic Table
• Sept. 1860 Karlsruhe, Germany
• Mendeleev- created a table in order of
  increasing atomic mass
• His table had the elements with similar
  properties grouped together
• Predicted new elements
Mendeleev uses density (a physical property) of atoms,
and organizes them in order of increasing atomic mass.

     There is a pattern!
  Moseley and the Periodic Law
• Two questions about Mendeleev’s
  table.
• 1. Why could you arrange most
  elements in order of increasing atomic
  mass, but a few could not?
• 2. What was the reason for chemical
  periodicity
   Moseley and the Periodic Law
• Discovered the total positive charge
  on the atom’s Atomic #
• When arranged by positive charge
  the arrangement was much
  improved.
       THE PERIODIC LAW
• The physical and chemical properties
  of the elements are periodic
  functions of their atomic numbers.
    The Modern Periodic Table
• An arrangement of the elements in
  order of their atomic numbers so
  that elements with similar properties
  fall in the same column
           Noble Gases
• Ramsey and Strutt - discovered
  Argon
• Ramsey found Helium, Krypton,
  Xenon
• This added a new group to the
  table.
               Lanthanides
• The Lanthanides – were completed in the
  early 1900’s
• They are the 14 elements found at the bottom
  of the table from # 58 - # 71
• These elements make up their own group
  because they are so similar in nature
                 Actinides
• The actinides are elements that are found on
  the bottom of the periodic table from
  # 90 to # 103
• These elements are so similar in
  characteristics that they make up their own
  group
• The lanthanides and the actinides contain
  radioactive elements
    Periods and Blocks of the Periodic Table

•   Horizontal rows- Periods
•   1st row - 1s is being filled
•   2nd row - 2s and 2p are filled
•   3rd row - 3s and 3p are filled
•   4th row - 4s then 3d then 4p are filled
•   5th row - 5s then 4d then 5p are filled
•   6th row - 6s then 4f then 5d then 6p filled
                   Assignment

• On the second section of that sheet of
  paper, please write six things that you
  learned from your notes so far that could
  appear on your test.
             Groups 1 and 2
• S- block groups 1 and 2
• Group 1 – alkali metals
• Group 2 – alkaline-earth metals
         Hydrogen and Helium
• Hydrogen - unique element
• The properties are not like any other element
• Sometimes hydrogen acts like a metal, and
  sometimes like a nonmetal
• Helium - inert gas
• Helium is unreactive in nature
                  The d- block
•   Groups 3 - 12
•   Metals with typical metal properties
•   Often called transition elements
•   Usually have 1, 2, or 3 electrons in their outer
    shell
                    The p - block
•   Groups 13 -18
•   s block and p block called the main block elements.
•   Properties vary greatly
•   Nonmetals
•   Metalloids
•   Metals
•   Halogens- F, Cl, Br, I, At
                 The f- block
•   Lanthanides
•   Actinides
•   Occur between groups 3 and 4
•   Fill f sublevels
•   Most of them are radioactive and synthetic
Atomic Radii – period and group trends
• Atomic Radii is the distance from the nucleus of one
  atom to the nucleus of the second bonded atom
• The smaller the atomic radii, the stronger the bond
• As you go from left to right, the atomic radius
  decreases (generally) Period trend
• As you go from top to bottom, the atomic radius
  increases (due to atomic sheltering) Group trend
                                   Atomic radius




        Increasing atomic number




Like for density, there is a repeating
       pattern in atomic radii.
                Ionization Energy

• Ionization energy deals with the ability of an atom to give
  up an electron (increases as you go across the period,
  and decreases as you go down the groups)
• A + energy ------à A+ + e-
• Any process that results in an ion being formed is called
  ionization
• Metals have lower energies than non metals because
  they want to get rid of their electrons
• The following charts deals with IE (first ionization energy)
                                       Ionization energy
ionization energy: the energy required to remove an
electron from an atom.




       low                                  high
               Electron Affinity
• Electron affinity is the energy that occurs when a
  neutral atom acquires an electron to become an ion
• A + e- ------à A- + energy
• Out of all the elements in the periodic table group 17
  (the halogens gain electrons the easiest)
• Metals have a lower number because they want to
  lose electrons and not gain electrons
                   Assignment

• On the third section of that sheet of
  paper, please write six things that you
  learned from your notes so far that could
  appear on your test.
Notice group 2, group 12, and group 18
                Electronegativity
• Electronegativity – is the measure of the ability of an
  atom in a chemical compound to attract electrons
• Nonmetals have a higher number because they want
  electrons
• If you subtract the lower number from the higher
  number you get a value that can be used with a table
  to indentify the type of bond
   – Ionic (between 3.3 and 1.7)
   – Polar-covalent (between 1.7 and 0.3)
   – Nonpolar covalent (between 0.3 and 0)
– Ionic (between 3.3 and 1.7)

– Polar-covalent (between 1.7 and 0.3)

– Nonpolar covalent (between 0.3 and 0)
                                           Electronegativity
electronegativity: the ability of an atom to attract another
atom’s electrons when bound to that other atom.




        low                                    high
           Assignment 6-1

• Write a three dollar summary paragraph
  about what you learned in this section
  along with answering the questions
  below.
• Turn to page 192 and answer # 1- 8 on a
  separate sheet of paper.

• Honors Chemistry Homework:
    page 192 # 12 - 20
           Vocabulary Section 2
•   Alkali metals
•   Alkaline earth metals
•   Transition metals
•   Halogens
•   Noble gases
    Quantum Numbers & Atomic Orbitals

•   Principal- dist.-n = 1,2,3,4,5,6,7
•   Orbital - shape- s , p, d, f
•   Magnetic- orientation 1,3,5,7
•   Spin- spin- +1/2, - ½
• The elements in Group 1, alkali metals, reacts easily because
  they lose electrons easily.
• Lithium, sodium, and potassium are the most abundant of the
  alkali metals and they always have a”+” charge
• All alkali metals have one electron in their highest unfilled
  outer shell
• All alkali metals combine with oxygen in a 2:1 ratio (Na2O, or
  Li2O)
• All alkali metals combine with halogens in a 1:1 ratio (NaCl, or
  KCl)
• Alkali metals are soft and react explosively with water but
  their ions are used by the body in nerve signaling, water
  retention, and maintaining correct blood chemistry levels
Alkali metals
• Group two metals, alkaline metals, form positive ions (+2)
  since their highest unfilled outer shell has only 2 electrons
• The most common of the alkaline metals are beryllium,
  magnesium, and calcium
• The alkaline metals combine with oxygen in a 1:1 (NaO, or
  KO) ratio and combine with the halogens in a 1:2 ratio NaCl2
  or KCl2)
• Magnesium and calcium are crutial to life
• Mg and Ca are needed for enzyme functions
• Calcium is important for teeth, bones and also helps maintain
  electrical impulses and magnesium assist enzymes in the body
Alkaline earth metals
                 Transition Metals
• The transition metals are at the center of the periodic table
  and include metals like titanium, chromium, nickel, and
  copper
• All transition metals are solids at room temperature except
  mercury
• They are excellent conductors of electricity
• Platinum is the most dense of all of the metals with a density
  of 21.45 g/cm3
• The transition metals start on the fourth row of the periodic
  table because they all have electrons in partly filled d orbitals
• There are no d orbitals in the first, second, and third rows of
  the periodic table
Transition metals
• Group 13 to 16 contains some extremely important elements
  such as:
   –  carbon which is the backbone of the chemistry of life
   – Nitrogen which is 78% of the earth’s atmosphere (N2)
   – Oxygen which makes up 21% of earth’s atmosphere (O2)
   – Both oxygen and nitrogen accept electrons and carbon can go both
     ways
   – All elements from group 13 to 16 have partially filled p orbitals which
     makes them very reactive
   – Oxygen has two spaces in the outer p orbital and so it works hard (is
     reactive) in order to get the last two
   – Nitrogen has three spaces in the outer p orbital and so it works hard
     (is reactive) to get those last three
                            Carbon, nitrogen, oxygen
        The electron structures makes these elements
               very flexible in their chemistry.




Carbon can accept or            Nitrogen and oxygen tend to
  donate electrons                    accept electrons
                   Assignment

• On the first section of the back side of
  paper, please write six things that you
  learned from your notes so far that could
  appear on your test.
                          Halogens
• Group 17 is known as the halogens and includes fluorine,
  chlorine, iodine, and bromine
• Halogens tend to be colorless gases at room temperature (if not a
  gas at room temperature, they form one easily when slightly
  heated
• The pure form of these gases are poisonous when inhaled, but
  the halogens in the ionic form is essential to life or to killing
  germs
• Unlike metals, halogens grab an electron which makes them
  negative in charge
• The halogens only have one free space in the p orbital and so
  they are extremely reactive in order to get that last electron
• In pure form, the halogens are diatomic (F2, Cl2, Br2, I2) and are
  highly toxic to microorganisms, bacteria and other living things
• Pure chlorine is a green gas that is foul smelling, but when
  combines with metals forms salts that can help life (NaCl)
Halogens
                         Noble Gases
• Group 18 is known as the noble gases (neon, helium, argon,
  krypton)
• They are called noble because they do not chemically bond
  with any other elements (with a 5 rare exceptions)
• The name came from the social class where the peasants
  were not allowed to interact with the noble class people
• When we look at the electron configuration of the noble
  gases it is easy to see why they do not react, they have full
  outer shells
• All other elements in the periodic table combine chemically to
  become perfect like the noble gases
• Two concepts can be learned form the noble gases:
   – Only electrons in an unfilled energy level are available to react and
     make bonds
   – Electrons in completely filled energy levels do not make bonds
Noble gases
Mendeleev left empty spaces for elements not yet discovered




    The first periodic table as suggested by Mendeleev in 1869
The modern periodic table
Electron structure was discovered after the periodic table was developed…
             ... but orbitals also follow a pattern in the periodic table.
  Element
   # 117
missing here
2009-2010

Element #117 was discovered through a Russian-US collaboration.
The discovery still needs to be confirmed.
It is temporarily named ununseptium (Uus).



            Discoveries are made all the time!
          Assignment 6-2

• Write a three dollar summary paragraph
  about what you learned in this section
  along with answering the questions
  below.

• Honors Chemistry Homework:
    page 192 # 21 - 29
         Vocabulary Section 3
• Valence electrons
• Lewis dot diagrams
• Electron configuration
Only the electrons in the highest unfilled energy level form chemical bonds.


  Does that mean we don’t need to worry about electrons in
  filled energy levels?


                                                 Yes!



              valence electrons: electrons in the highest unfilled energy
              level, responsible for making chemical bonds.
                     Remember that elements
Oxygen and sulfur    that belong to the same
belong to the same   group have similar chemical
group in the         properties!
periodic table
There are millions and millions of different kinds of matter
(compounds) composed of the same 92 elements.

These elements are organized in a periodic table.
It is called “periodic” because
there is a repeating pattern.

Elements that belong to the
same column have similar
chemical properties.

Here, we are going to go over
these groups of elements
Valence and Electron Configuration
• The electrons that are in the filled shells are not available for
  bonding
• Only the valence electrons can take part in the chemical
  bonding process
• Electron configuration and the electron dot diagrams are
  ways to identify the free electrons and the ones that are not
  available for bonding
• Metals in the same group react similarly since they have the
  same number of valence electrons in the outer shell
• Non metals in the same group react similarly since they have
  the same number of valence electrons in the outer shell
• Valence electrons are electrons found in the highest unfilled
  energy level (the ones available for chemical bonding)
Sulfur and oxygen have the same number of valence electrons.
They form similar chemical compounds.
    Quantum Numbers & Atomic Orbitals

•   Come from Schrodinger Equation
•   Indicate region occupied by orbital
•   1.Distance from nucleus
•   2. Orbital shape
•   3. Orbital position on x,y,z axis
    Quantum Numbers & Atomic Orbitals

•   Principal quantum number
•   . Symbolized by n
•   . indicates the main energy level
•   . average distance from nucleus
•   . referred to as shells
•   . n= 1,2,3,4,5,6,7
    Quantum Numbers & Atomic Orbitals

•   Orbital quantum number
•   . indicates shape
•   . called sublevels or subshells
•   . indicated by s, p, d, f
•   . s is spherical
•   . p is dumbbell shape.
         Quantum Numbers &
           Atomic Orbitals
•   Orbital cont.
•   . if n= 1 then only s is allowed
•   . if n= 2 then s and p
•   . if n = 3 then s and p and d
•   . if n = r then s, p, d, f
        Quantum Numbers &
          Atomic Orbitals
•   Magnetic quantum number
•   . orientation in space
•   . s -- one
•   . p -- three
•   . d -- five
•   . f -- seven
    Quantum Numbers & Atomic Orbitals

•   Principal- dist.-n = 1,2,3,4,5,6,7
•   Orbital - shape- s , p, d, f
•   Magnetic- orientation 1,3,5,7
•   Spin- spin- +1/2, - ½
                   Assignment

• On the second section of the back side of
  paper, please write six things that you
  learned from your notes so far that could
  appear on your test.
                        Determining valence electrons




•   Write down the electron configuration.




                  2     2     6     2        5
     Cl = 1s 2s 2p 3s 3p
                        Determining valence electrons




•   Write down the electron configuration.
•   Count how many electrons are in the highest s and p orbitals
    (it should be between 1 and 8).
•   These are the valence electrons.

                                    2 + 5 = 7 valence electrons

                  2     2     6     2        5
     Cl = 1s 2s 2p 3s 3p
                         Determining valence electrons




 •   Write down the electron configuration.
 •   Count how many electrons are in the highest s and p orbitals
     (it should be between 1 and 8).
 •   These are the valence electrons.
                                              2   +    1 = 3 valence
                                                             electrons
             2     2     6     2     6        2   10   1
Ga = 1s 2s 2p 3s 3p 4s 3d 4p
                             Lewis dot diagram for carbon




                                1s22s22p2
                                4 valence electrons


Lewis dot diagram: a diagram showing one dot for each
valence electron an atom has, these dots surround the
element symbol of the atom.
              Lewis dot diagrams

• A clever way to keep track of
  valence electrons is to draw
  Lewis dot diagrams.
• A dot diagram shows the
  element symbol surrounded
  by one to eight dots
  representing the valence
  electrons.

                                  What is the dot
                                  structure for nitrogen?
- Elements that belong to the same group in the   Carbon has
periodic table have the same number of valence    4 valence electrons
electrons

- Only valence electrons are involved in
chemical bonding

- The Lewis dot diagram is a way to show
valence electrons for an atom



        Lewis dot
        diagram
        for carbon   1s22s22p2
                     4 valence electrons
                     Try
• Complete the electron configuration for the
  following elements:
  – Cl
  –O
  – Ag
  – Li
  – Mg
  – Ca
Lewis dot diagram
           Assignment 6-3

• Write a three dollar summary paragraph
  about what you learned in this section
  along with answering the questions
  below.
• Turn to page 192 and answer # 9- 11 on a
  separate sheet of paper.

• Honors Chemistry Homework:
    page 192 # 30 - 39
     Test: - Next week Tuesday or Thursday
                depending on your class.



• Homework requirement: Learn all terms and
  concepts covered on this topic.

• Make sure you have all assignments between
  page 192 and 195 completed and turned in by
  your test date.

								
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