Docstoc

Atoms-Elements

Document Sample
Atoms-Elements Powered By Docstoc
					    Chapter 2        Atoms and Elements
2.1
Classification of Matter
     Matter
Matter
     Is the material that makes up a substance.
     Makes up the things we see everyday, such as water, wood, cooking pan, clothes, and shoes.

    Pure Substances
A pure substance is classified as
    Matter with a specific composition.
    An element when composed of one type of atom.
    A compound when composed of two or more elements combined in a definite ratio.

    Elements
Elements are
    Pure substances that contain atoms of only one type.
               Copper (Cu)
               Lead (Pb)
               Aluminum (Al)
    Compounds
Compounds
    Contain two or more elements in a definite ratio.
               Salt (NaCl)
               Table sugar (C12H22O11)
               Water (H2O)
    Elements in a Compound
       “Table salt” is a compound that contains the elements sodium and chlorine.
    Mixtures
A mixture is matter that consists of
    Two or more substances that are physically mixed, not chemically combined.
    Two or more substances in different proportions.
    Substances that can be separated by physical methods.

     Physical Separation of A Mixture
The physical separation of a mixture
     Involves only physical changes.
     Occurs when pasta and water are separated with a strainer.
     Homogeneous Mixtures
In a homogeneous mixture,
     The composition is uniform throughout.
     The different parts of the mixture are not visible.

                                                                                       1|Page
     Heterogeneous Mixtures
In a heterogeneous mixture,
     The composition is not uniform, it varies from one part of the mixture to another.
     The different parts of the mixture are visible.
     Classification of Matter
     Inquiry
        Identify each of the following as a pure substance or a mixture.
        A. pasta and tomato sauce
        B. aluminum foil
        C. helium
        D. air

       Solution
       Identify each of the following as a pure substance or a mixture.
       A. pasta and tomato sauce                mixture
       B. aluminum foil                         pure substance
       C. helium                                pure substance
       D. air                                   mixture

        Inquiry
Identify each of the following as a homogeneous or
heterogeneous mixture:
A. hot fudge sundae
B. shampoo
C. sugar water
D. peach pie
        Solution
Identify each of the following as a homogeneous or
heterogeneous mixture:
A. hot fudge sundae heterogeneous mixture
B. shampoo                      homogeneous mixture
C. sugar water           homogeneous mixture
D. peach pie             heterogeneous mixture



    Chapter 2         Atoms and Elements
2.2
Elements and Symbols
     Elements
Elements are
     Pure substances that cannot be separated into simpler substances by ordinary laboratory
       processes.

                                                                                           2|Page
      The building blocks of matter.
         gold            carbon         aluminum

     Sources of Some Element Names
Some elements are
named for planets,
mythological figures,
minerals, colors,
scientists, and
places.
     Symbols of Elements
A symbol
     Represents the name of an element.
     Consists of 1 or 2 letters.
     Starts with a capital letter.

       Examples:
              1-Letter Symbols                2-Letter Symbols
              C carbon                        Co      cobalt
              N nitrogen                      Ca      calcium
              F fluorine                      Al      aluminum
              O oxygen                        Mg      magnesium
     Symbols from Latin Names
Some symbols are derived from Latin names as shown
below:
       Cu, copper (cuprum)            Au, gold (aurum)

        Fe, iron (ferrum)                    Ag, silver (argentum)

     Physical Properties of Elements
The physical properties of an element
     Are observed or measured without changing its identity.
     Include the following:
                Shape
                Color
                Odor
     Taste
                Density
                Melting point
                Boiling Point
     Physical Properties of Elements
Some physical properties of

                                                                     3|Page
copper are:
Color                     Red-orange
Luster                    Very shiny
Melting point             1083°C
Boiling point             2567°C
Conduction
of electricity            Excellent
Conduction
of heat           Excellent
      Inquiry
Select the correct symbol for each:
A. Calcium
          1) C            2) Ca                 3) CA
B. Sulfur
          1) S            2) Sl                 3) Su
C. Iron
          1) Ir           2) FE                 3) Fe
      Solution
Select the correct symbol for each:
A. Calcium
          2) Ca
B. Sulfur
          1) S
C. Iron
          3) Fe
      Inquiry
Select the correct name for each symbol:
A. N
          1) neon                   2) nitrogen       3) nickel
B. P
          1) potassium 2) phlogiston 3) phosphorus
C. Ag
          1) silver                 2) agean          3) gold
      Solution
Select the correct name for each:
A. N
           2) nitrogen
B. P
           3) phosphorus
C. Ag
           1) silver


                                                                  4|Page
     Chapter 2 Atoms and Elements
     Groups and Periods
On the periodic table
     Groups contain elements with similar properties in vertical columns.
     Periods are horizontal rows of elements.
     Groups and Periods




     Periodic Table



    Group Numbers
Group Numbers
    Use the letter A for the representative elements (1A to 8A) and the letter B for the transition
       elements.
    Also use numbers 1-18 to the columns from left to right.
    Representative Elements
    Several groups of representative elements are known by common names.

     Alkali Metals
         Group 1A(1), the alkali metals, includes lithium, sodium, and potassium.
     Halogens
         Group 7A(17), the halogens, includes chlorine, bromine, and iodine.
     Learning Check
Identify the element described by the following:
A. Group 7A(17), Period 4
          1) Br         2) Cl                      3) Mn


                                                                                             5|Page
B. Group 2A(2), Period 3
           1) beryllium 2) magnesium             3) boron
C. Group 5A(15), Period 2
           1) phosphorus 2) arsenic              3) nitrogen
      Solution
A. Group 7A (17), Period 4
                  1) Br
B. Group 2A (2), Period 3
                  2) magnesium
C. Group 5A(15), Period 2
                  3) nitrogen
      Metals, Nonmetals, and Metalloids
The heavy zigzag line
separates metals and
nonmetals.
      Metals are located to the left.
      Nonmetals are located to the right.
      Metalloids are located along the heavy zigzag line between the metals and nonmetals.
      Properties of Metals, Nonmetals, and Metalloids
Metals
      Are shiny and ductile.
      Are good conductors of heat and electricity.
Nonmetals
      Are dull, brittle, and poor conductors of heat and electricity.
      Are good insulators.
Metalloids
      Are better conductors than nonmetals, but not as good as metals.
      Are used as semiconductors and insulators.
      Comparing A Metal, Metalloid, and Nonmetal
      Learning Check
Identify each of the following elements as
1) metal          2) nonmetal      3) metalloid
A. sodium         ____
B. chlorine       ____
C. silicon        ____
D. iron           ____
E. carbon         ____
      Solution
Identify each of the following elements as
1) metal          2) nonmetal      3) metalloid
A. sodium                  1 metal
B. chlorine                2 nonmetal

                                                                                          6|Page
C. silicon               3 metalloid
D. iron                  1 metal
E. carbon                2 nonmetal
      Learning Check
Match the elements to the description:
A. Metals in Group 4A(14)
          1) Sn, Pb      2) C, Si         3) C, Si, Ge, Sn
B. Nonmetals in Group 5A(15)
           1) As, Sb, Bi 2) N, P 3) N, P, As, Sb
C. Metalloids in Group 4A(14)
           1) C, Si, Ge, 2) Si, Ge        3) Si, Ge, Sn, Pb
      Solution
Match the elements to the description:
A. Metals in Group 4A (14)
         1) Sn, Pb
B. Nonmetals in Group 5A(15)
          2) N, P
C. Metalloids in Group 4A(14)
          2) Si, Ge




    
        Chapter 2 Atoms and Elements
     Atomic Number
The atomic number
     Is specific for each element.
     Is the same for all atoms of an element.
     Is equal to the number of protons in an atom.
     Appears above the symbol of an element.
     Atomic Number and Protons
Examples of atomic number and number of protons:
     Hydrogen has atomic number 1, every H atom has one proton.
     Carbon has atomic number 6, every C atom has six protons.
     Copper has atomic number 29, every Cu atom has 29 protons.
     Gold has atomic number 79, every Au atom has 79 protons.
     Learning Check
State the number of protons in each.
A. A nitrogen atom
         1) 5 protons     2) 7 protons         3) 14 protons
B. A sulfur atom
         1) 32 protons 2) 16 protons           3) 6 protons

                                                                   7|Page
C. A barium atom
         1) 137 protons           2) 81 protons         3) 56 protons
     Solution
State the number of protons in each.
A. A nitrogen atom
         2) atomic number 7; 7 protons
B. A sulfur atom
         2) atomic number 16; 16 protons
C. A barium atom,
         3) atomic number 56; 56 protons
     Number of Electrons in An Atom
An atom
     Of an element is electrically neutral; the net charge of an atom is zero.
     Has an equal number of protons and electrons.
                number of protons = number of electrons
     Of aluminum has 13 protons and 13 electrons. The net charge is zero.
    13 protons (13+) + 13 electrons (13 -) = 0
     Mass Number
The mass number
     Represents the number of particles in the nucleus.
     Is equal to the
                  Number of protons + Number of neutrons
     Atomic Models
     Learning Check
An atom of zinc has a mass number of 65.
A. How many protons are in this zinc atom?
         1) 30         2) 35                    3) 65
B.       How many neutrons are in the zinc atom?
         1) 30         2) 35                    3) 65
C. What is the mass number of a zinc atom that has
   37 neutrons?
         1) 37         2) 65                    3) 67
     Solution
An atom of zinc has a mass number of 65.
A. How many protons are in this zinc atom?
                 1) 30          (atomic number 30)

B.      How many neutrons are in the zinc atom?
                2) 35          (65 – 30 = 35)
C. What is the mass number of a zinc atom that has 37 neutrons?
                3) 67          (30 + 37 = 67)
     Learning Check

                                                                                  8|Page
An atom has 14 protons and 20 neutrons.
A. Its atomic number is
          1) 14         2) 16               3) 34
B. Its mass number is
          1) 14         2) 16               3) 34
C. The element is
          1) Si         2) Ca               3) Se

     Solution
An atom has 14 protons and 20 neutrons.
A. It has atomic number
          1) 14
B. It has a mass number of
          3) 34 (14 + 20 = 34)
C. The element is
          1) Si (Atomic number 14)




       Chapter 2     Atoms and Elements
2.6




Isotopes and Atomic Mass
     Isotopes
Isotopes
     Are atoms of the same element that have different mass numbers.
     Have the same number of protons, but different numbers of neutrons.
     Nuclear Symbol


                                                                            9|Page
A nuclear symbol
     Represents a particular atom of an element.
     Gives the mass number in the upper left corner and the atomic number in the lower left corner.
   Example: An atom of sodium with atomic number 11 and a mass number 23 has the following atomic
symbol:
                mass number 23 Na
                atomic number 11
     Nuclear Symbols
For an atom, the nuclear symbol gives the number of
     Protons (p+)
     Neutrons (n)
     Electrons (e-)
          16                    31                       65

     O             P                      Zn
           8                    15                       30




          8 p+          15 p+                    30 p+
          8n            16 n                     35 n
             -               -
          8e            15 e                     30 e-
    Learning Check
 Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons,
neutrons, and electrons in each of the following.
                         12              13              14
                           C               C               C
                   6             6               6

      protons      ______ ______      ______
      neutrons ______ ______      ______
      electrons    ______ ______      ______
     Solution
                    12        13             14
                      C         C              C
                   6             6               6

      protons          6 p+           6 p+             6 p+
      neutrons 6 n           7n              8n
                          -              -
      electrons        6e             6e              6 e-
     Learning Check
      Write the nuclear symbols for atoms with the following subatomic particles:
      A. 8 p+, 8n, 8e-       ___________
             +          -
      B. 17p , 20n, 17e      ___________

         C. 47p+, 60 n, 47 e-   ___________



     Solution

                                                                                             10 | P a g e
                                        16
                                            O
                  +            -        8
         A. 8p , 8n, 8e

         B. 17p+, 20 n, 17e-           37
                                            Cl
                                       17

         C. 47p+, 60n, 47e-            107
                                             Ag
                                        47




     Learning Check
1. Which of the following pairs are isotopes of the same element?
2. In which of the following pairs do both atoms have
   8 neutrons?
A. 15X           15
                   X
     8                    7

         12           14
B.            X           X
              6       6

          15          16
C.            X            X
          7            8

      Solution
       12      14
B.       X       X
          6           6

       Both nuclear symbols represent isotopes of carbon with six protons each, but one has 6
neutrons and the other has 8.
        15      16
C.        X       X
          7            8

   An atom of nitrogen (7) and an atom of oxygen (8) each have 8 neutrons.
     Isotopes of Magnesium
In naturally occurring magnesium,
there are three isotopes.

      Isotopes of Sulfur
A sample of naturally
occurring sulfur contains
several isotopes with the
following abundances
Isotope % abundance
32
  S              95.02
33
  S               0.75
34
  S               4.21
36
  S               0.02
      Atomic Mass
The atomic mass of an element

                                                                                         11 | P a g e
      Is listed below the symbol of each element on the periodic table.
      Gives the mass of an “average” atom of each element compared to 12C.
      Is not the same as the mass number.
      Some Elements and Their Atomic Mass

      Atomic Mass for Cl
The atomic mass of chlorine is
      Based on all naturally occurring Cl isotopes.
      Not a whole number.
      The weighted average
         of 35Cl and 37Cl.
      Learning Check
Using the periodic table, give the atomic mass of
each element:
A.       calcium           __________
B. aluminum                __________
C. lead           __________
D. barium                  __________
E. iron                    __________
      Solution
Using the periodic table, give the atomic mass of
each element:
A.        calcium                 40.08 amu
B. aluminum                26.98 amu
C. lead           207.2 amu
D. barium                  137.3 amu
E. iron           55.85 amu
      Chapter 2 Atoms and Elements
2.7
Electron Energy Levels
      Electromagnetic Radiation
Is energy that travels as waves through space.
Is described in terms of wavelength and frequency.
Moves at the speed of light in a vacuum.
speed of light = 3.0 x 108 m/s
      Electromagnetic Spectrum
The electromagnetic spectrum
      Arranges forms of energy from lower to higher.
      Arranges energy from longer to shorter wavelengths.
      Shows visible light with wavelengths from 700-400 nm.



                                                                              12 | P a g e
      Learning Check
1. Which of the following has the shortest wavelength?
   A. microwaves         B. blue light           C. UV light
2. Which of the following has the lowest energy?
   A. red light B. blue light            C. green light
      Solution
1. Which of the following has the shortest wavelength?
   C. UV light
2. Which of the following has the lowest energy?
   A. red light
      Spectra
White light that passes
through a prism
      is separated into all colors called a continuous spectrum.
      Gives the colors of a rainbow.




                                                                    13 | P a g e
     Atomic Spectrum
An atomic spectrum consists of
     Lines of different colors formed when light from a heated element passes through a prism.
     Photons emitted when electrons drop to lower energy levels.

     Electron Energy Levels
Electrons are arranged in
specific energy levels that
     Are labeled n = 1, n = 2, n = 3, and so on.
     Increase in energy as n increases.
     Have the electrons with the lowest energy in the first energy level (n=1)closest to the nucleus.
     Energy Level Changes
     An electron absorbs energy to “jump” to a higher energy level.
     When an electron falls to a lower energy level, energy is emitted.
     In the visible range, the emitted energy appears as a color.




 Energy Emitted
      Learning Check
In each of the following energy level changes, indicate
if energy is
1) absorbed              2) emitted      3) not changed
A. An electron moves from the first energy level (n =1 ) to the third energy level (n = 3).
B. An electron falls from the third energy level to the second energy level.
C. An electron moves within the third energy level.

    Solution
A. An electron in an atom moves from the first energy level (n =1 ) to the third energy level (n = 3).
               1) absorbed
B. An electron falls from the third energy level to the second energy level.
               2) emitted

                                                                                              14 | P a g e
C. An electron moves within the third energy level.
               3) not changed
     Sublevels
Sublevels
     Contain electrons with the same energy.
     Are found within each energy level.
     Are designated by the letters s, p, d, f.
  The number of sublevels is equal to the value of the principal quantum number (n).

     Number of Sublevels




     Energy of Sublevels
In any energy level,
     The s sublevel has the lowest energy.
     The s sublevel is followed by the p, d, and f sublevels in order of increasing energy.
     Higher sublevels are possible, but only s, p, d, and f sublevels are needed to hold the electrons in
        the atoms known today.
     Orbitals




     s Orbitals

                                                                                             15 | P a g e
        p Orbitals




A p orbital
     Has a two-lobed shape.
     Is one of three p orbitals that make up each p sublevel.
     Increases in size as the value of n increases.

         Sublevels and Orbitals
Each sublevel consists of a specific number of
orbitals.
     An s sublevel contains one s orbital.
     A p sublevel contains three p orbitals.
     A d sublevel contains five d orbitals.


                                                                 16 | P a g e
          An f sublevel contains seven f orbitals.




           Electrons in Each Sublevel




      Learning Check
Indicate the number and type of orbitals in each of the
following:
A. 4s sublevel
B. 3d sublevel
C. n = 3

     Solution
A. 4s sublevel
                    one 4s orbital
B. 3d sublevel
                   five 3d orbitals
C. n = 3
           one 3s orbital, three 3p orbitals,
                   and five 3d orbitals


                                                          17 | P a g e
     Learning Check
The number of
       A. electrons that can occupy a p orbital is
                1) 1              2) 2            3) 3
       B. p orbitals in the 2p sublevel is
                1) 1              2) 2            3) 3
       C. d orbitals in the n = 4 energy level is
                1) 1              2) 3            3) 5
       D. electrons that can occupy the 4f sublevel are
                1) 2              2) 6            3) 14
     Solution
The number of
       A. electrons that can occupy a p orbital is
                2) 2
       B. p orbitals in the 2p sublevel is
                3) 3
       C. d orbitals in the n = 4 energy level is
                3) 5
       D. electrons that can occupy the 4f sublevel are
                3) 14




     Chapter 2 Atoms and Elements
2.8     Electron Configurations         Order of Filling
Energy levels are filled with electrons
     In order of increasing energy.
     Beginning with quantum number n = 1.
     Beginning with s followed by p, d, and f.
Energy Diagram for Sublevels




                                                           18 | P a g e
        Orbital Diagrams
An orbital diagram shows
     Orbitals as boxes in each sublevel.
     Electrons in orbitals as vertical arrows.
     Electrons in the same orbital with opposite spins (up and down vertical arrows).
        Orbital diagram for Li
                                          1s2   2s1     2p
                           filled half-filled empty
     Order of Filling
Electrons in an atom
     Fill orbitals in sublevels of the same type with one electron until half full,
     Then pair up in the orbitals using opposite spins.

      Writing Orbital Diagrams
The orbital diagram
for carbon consists of
      Two electrons in the 1s orbital.
      Two electrons in the 2s orbital.
      One electron each in two of the 2p orbitals.
      Learning Check
Write the orbital diagrams for
A. carbon
B. oxygen
C. magnesium
      Solution

                                                                                         19 | P a g e
Write the orbital diagrams for
A. carbon
                          1s      2s       2p
B. oxygen
                          1s      2s       2p
C. magnesium
                          1s      2s       2p        3s
     Electron Configuration
An electron configuration
     Lists the sublevels filling with electrons in order of increasing energy.
     Uses superscripts to show the number of electrons in each sublevel.
     For neon is as follows:
                          number of electrons
         sublevel      2  2
                     1s 2s 2p6

     Period 1 Configurations
In Period 1, the first two electrons enter the 1s orbital
     Abbreviated Configurations
An abbreviated configuration shows
     The symbol of the noble gas in brackets that represents completed sublevels.
     The remaining electrons in order of their sublevels,
         Example: Chlorine has a configuration of
           1s2 2s2 2p6 3s2 3p5
        [Ne]
         The abbreviated configuration for chlorine is
          [Ne] 3s2 3p5




     Period 2 Configurations




                                                                                     20 | P a g e
     Period 3 Configurations




     Learning Check
A. The correct electron configuration for nitrogen is
        1) 1s2 2p5      2) 1s2 2s2 2p6 3) 1s2 2s2 2p3
B. The correct electron configuration for oxygen is
        1) 1s2 2p6      2) 1s2 2s2 2p4 3) 1s2 2s2 2p6
C. The correct electron configuration for calcium is


                                                        21 | P a g e
          1) 1s2 2s2 2p6 3s2 3p6 3d2
          2) 1s2 2s2 2p6 3s2 3p6 4s2
          3) 1s2 2s2 2p6 3s2 3p8
      Solution
A. The correct electron configuration for nitrogen is
                   3) 1s2 2s2 2p3
B. The correct electron configuration for oxygen is
                   2) 1s2 2s2 2p4
C. The correct electron configuration for calcium is
                   2) 1s2 2s2 2p6 3s2 3p6 4s2
      Learning Check
          Write the electron configuration and abbreviated configuration for each of the following
elements:
          A. Cl
          B. S
          C. K
      Solution
A. Cl
           1s2 2s2 2p6 3s2 3p5                 [Ne] 3s23p5
B. S
           1s2 2s2 2p6 3s2 3p4                 [Ne] 3s2 3p4
C. K
            1s2 2s2 2p6 3s2 3p6 4s1            [Ar]4s1
      Sublevel Blocks on the
          Periodic Table
The periodic table consists of sublevel blocks
arranged in order of increasing energy.
      Groups 1A(1)-2A(2)            = s level
      Groups 3A(13)-8A(18) = p level
      Groups 3B(3) to 2B(12) = d level
      Lanthanides/Actinides = f level
      Sublevel Blocks
      Using Sublevel Blocks
      Writing Electron Configurations
Using the periodic table, write the electron configuration
for silicon.
Solution
Period 1           1s block                    1s2
Period 2           2s → 2p blocks              2s2 2p6
                                       2     2
Period 3           3s → 3p blocks 3s 3p (at Si)
Writing all the sublevel blocks in order gives:
                   1s2 2s2 2p63s2 3p2

                                                                                             22 | P a g e
     Electron Configurations d Sublevel
     The 4s orbital has a lower energy than the 3d orbitals.
     In potassium K, the last electron enters the 4s orbital instead of the 3d
                          1s      2s 2p 3s 3p 3d          4s
                             2      2   6    2  6
        Ar                1s      2s 2p 3s 3p
        K                 1s2     2s2 2p6 3s2 3p6 4s1
        Ca                1s2     2s2 2p6 3s2 3p6 4s2
        Sc                1s2     2s2 2p6 3s2 3p6 3d1     4s2
        Ti                1s2     2s2 2p6 3s2 3p6 3d2     4s2
     Writing Electron Configurations
Using the periodic table, write the electron configuration
for manganese.
Solution
Period 1         1s block                 1s2
Period 2         2s → 2p blocks           2s2 2p6
Period 3         3s → 3p blocks 3s2 3p6
Period 4         4s → 3d blocks 4s2 3d5 (at Mn)
Writing all the sublevel blocks in order gives:
       1s2 2s2 2p63s2 3p6 4s2 3d5
     4s Block
     3d Block
     4p Block

     Learning Check
     Solution
     Learning Check
         Using the periodic table, write the electron configuration and abbreviated configuration for each
of the following elements:
         A. Cd
         B. Sr
         C. I
     Solution
A. Cd
           1s2 2s2 2p6 3s2 3p6 4s2 3d10
          [Kr] 4s2 3d10
B. Sr
           1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
          [Kr] 5s2
C. I
           1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5
           [Kr] 5s2 4d10 5p5
     Learning Check

                                                                                             23 | P a g e
Give the symbol of the element that has
A. [Ar]4s2 3d6
B. Four 3p electrons
C. Two electrons in the 4d sublevel
D. The element that has the electron configuration
        1s2 2s2 2p6 3s2 3p6 4s2 3d2

      Solution
Give the symbol of the element that has
A. [Ar]4s2 3d6                              Fe
B. Four 3p electrons                        S
C. Two electrons in the 4d sublevel         Zr
D. Electron configuration                           Ti
      2   2  6  2   6   2    2
    1s 2s 2p 3s 3p 4s 3d
      Chapter 2 Atoms and Elements
2.9
Periodic Trends
      Valence Electrons
The valence electrons
      Determine the chemical properties of the elements.
      Are the electrons in the highest energy level.
      Are related to the Group number of the element.
Example: Phosphorus has 5 valence electrons
                                             5 valence electrons
                P Group 5A(15)            2
                                       1s 2s2 2p6 3s2 3p3
      Groups and Valence Electrons
All the elements in a group have the same number of
valence electrons.
Example: Elements in Group 2A(2) have two (2)                  valence electrons.
                            2   2
                Be        1s 2s
                Mg        1s2 2s2 2p6 3s2
                Ca        [Ar] 4s2
                Sr        [Kr] 5s2
      Periodic Table and Valence Electrons




                                                                                    24 | P a g e
     Learning Check
State the number of valence electrons for each:
        A. O
               1) 4            2) 6             3) 8
        B. Al
               1) 13           2) 3             3) 1
        C. Cl
               1) 2            2) 5             3) 7

     Solution
State the number of valence electrons for each.
        A. O
               2) 6
        B. Al
               2) 3
        C. Cl
               3) 7

     Learning Check
State the number of valence electrons for each.
A. Calcium
         1) 1          2) 2             3) 3
B. Group 6A (16)
         1) 2          2) 4             3) 6

                                                       25 | P a g e
C. Tin
           1) 2          2) 4             3) 14
      Solution
State the number of valence electrons for each.
A. Calcium
         2) 2
B. Group 6A (16)
         3) 6
C. Tin
         2) 4
      Learning Check
State the number of valence electrons for each.
A. 1s2 2s2 2p6 3s2 3p1
B. 1s2 2s2 2p6 3s2
C. 1s2 2s2 2p5
      Solution
State the number of valence electrons for each.
A. 1s2 2s2 2p6 3s2 3p1   3
      2  2    6  2
B. 1s 2s 2p 3s                    2
C. 1s2 2s2 2p5           7
      Electron-Dot Symbols
An electron-dot symbol
      Indicates valence electrons
         as dots around the symbol of the element.
      Of Mg shows two valence electrons as single dots on the sides of the symbol Mg.
                       .       .
· Mg · or Mg · or · Mg or · Mg
                                     ·
      Writing Electron-Dot Symbols
The electron-dot symbols for
      Groups 1A(1) to 4A(14) use single dots.
                                        ·         ·
    Na ·        · Mg ·     · Al · · C ·
                                                    ·
      Groups 5A(15) to 7A(17) use pairs and single dots.
           ··              ··
   · P· :O ·
   ·          ·
      Groups and Electron-Dot Symbols
      In a group, all the electron-dot symbols have the same number of valence electrons (dots).
   Example: Atoms of elements in Group 2A(2) each have 2 valence electrons.
                   2A(2)

                                                                                          26 | P a g e
              · Be ·
              · Mg ·
              · Ca ·
              · Sr ·
              · Ba ·
    Learning Check
    
A. X is the electron-dot symbol for
                       1) Na          2) K    3) Al
   
B.  X 
             is the electron-dot symbol of

                       1) B           2) N    3) P

    Solution
          
A. X is the electron-dot symbol for
                       1) Na          2) K
    
B.  X 
     is the electron-dot symbol of
               2) N           3) P

    Atomic Size




                                                      27 | P a g e
     Atomic Radius Within A Group
Atomic radius
     Increases going down each group of representative elements.
     Decreases going across each period.
     Learning Check
Select the element in each pair with the larger atomic
radius.
A. Li or K
B. K or Br
C. P or Cl
     Solution
Select the element in each pair with the larger
atomic radius.
A. K
B. K
C. P
     Ionization Energy
Ionization energy

                                                                    28 | P a g e
       Is the energy it takes to remove a valence electron.

                Na(g) + Energy (ionization)         Na+(g) + e-

     Ionization Energy
The ionization
energies of
     Metals are low.
     Nonmetals are high.
     Learning Check
Select the element in each pair with the higher
Ionization energy.
A. Li or K
B. K or Br
C. P or Cl
     Solution
Select the element in each pair with the higher
Ionization energy.
A. Li
B. Br
C. Cl




                                                                  29 | P a g e

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:22
posted:11/29/2011
language:English
pages:29