Electronic Structure (Electron Dot Diagrams)

Drawing electron dot diagrams:

• the nucleus is rapresented by the atomic symbol 
• for individual elements determine the numebr of valence electrons
• electrons are rapresented by dots around the symbol
• four orbitals (one of each side of the nucleus) each holding a maximum of 2 electorns
• each orbital gets 1 electron before they pair up 

example: draw the Lewis Dot Diagram for the following elements

• Si

• Hydrogen

• Xenon

• Chlorine

Lewis Diagram for compounds & ions:

• in covalent compounds electrons are shared

1. Dteremine the number of valence electrons for each atom in the molecule
2. Place atoms so that valence electrons are shared to fill each orbital

example: draw the Lewis Dot Diagram for the following compaunds

• MgCl2

dot diagram

line diagram

• Li3N

Double & Triple Bonds:

example:

• NOCl

• HCN

 Ionic Compounds:

• in ionic compounds elecrons transfer from one element to another
• determine the number of valence electrons on the cation, move these to the anion
• draw [ ] around the metal and non-metal
• write the charges outside the brackets

example:

• calcium fluoride

• sodium chloride

-Eva

Trends on the Periodic Table

I. Elements close to each other on the periodic table display similar characteristics
     A. There are 7 important periodic trends
          1. Reactivity
          2. Ion Charge
          3. Melting Point
          4. Atomic Radius
          5. Ionization Energy
          6. Electronegativity
          7. Density*

II. REACTIVITY
     A. Metals and non-metals show different trends
          1. The most reactive elements are located on the outside of the periodic table
          2. The elements on the inner part of the table are the least reactive
          3. Note that noble gases are not reactive

III. Ion Charge
     A. Elements ion charges depend on their group (column)


IV. Melting Point
     A. Elements in the center of the table have to highest melting point
     B. Elements closest to the outer edges have the lowest melting point
     C. Noble gases have the lowest melting point

V. Atomic Radius
     A. The atomic radius gets smaller and smaller as you move up and to the right

     C. Francium has the largest atomic radius

VI. Ionization Energy

     A. Energy required to move an electron from an atom

     B.Ionization energy increases going from the right and going up

     C. All noble gases have a high ionization energy

     D. Helium has the highest ionization energy/ Francium has the lowest ionization energy

VII. Electronegativity

     A. Electronegativity: how much atoms want to gain electrons

     B. It increases going up and to the right

-Nicole P

Isotopes and Atoms

• atomic number (number of protons)

            atomic number -->    8     2- --> ion charge
            symbol -->   O                 
                  name -->   Oxygen  
          atomic mass  -->   16.0

• atomic mass - atomic number = number of neutrons

         (p+n)         -       (p)           =      (n)

•  1    --> atomic number - Z              1           1          1

       H                         H     H    H
    1    --> mass number - A                1            2         3

• example:  fill in the table

Isotope	Mass number	Atomic number	Number of                      protons	Number  of neutrons
3       H	3	1	1	2
57    Co	57	27	27	30
234   U	234	92	92	144
18     O	18	8	8	10

• mass spectrometers:

          are used to determine the abundance and mass of the isotopes of 

          elements

-Eva

Quantum Mechanics

I. Bohr Theory
     A. The electron is a particle that must be in orbital in the atom
II. Quantum Theory
     A. The electron is a cloud of negative charge or a wave function
     B. Orbitals are areas in 3d space where the electrons most probably are
     C. The energy of the electron is in its vibrational modes
     D. Photons sre produced when high energy modes change to lower energy modes

S ORBITALS
-each orbital holds 2 electrons

P ORBITALS
-3 suborbitals
-each  orbital holds 2 electron
-muximum of 6 electrons

D ORBITALS
-5 suborbitals
-each orbital can hold 2 electrons
-maximum of 10 electrons

F ORBITALS
-7 suborbitals
-each orbital can hold 2 electrons
-maximum of 14 electrons


EXAMPLES:
1. How many and what type of electrons does an atom of arsenic have?

electrons= 33

1s²2s²2p⁶3s²3p⁶4s³

^{2. How many and what type of electrons does an atom of zirconium have?}

^{electrons= 40}

1s²2s²2p⁶3s²3p⁶4s⁶5s²4d²

^{3. How many and what type of electrons does an ion of Magnesium with a charge of 2+ have?}

^electrons=10

1s²2s²2p⁶

^{4. How many and what type of electrons does an atom of neon have?}

^{electrons= 10}

1s²2s²2p⁶

<sup>Magnesium 2+ and neon both have the same electron configuration. This means they are isoelectronic.




-nicole</sup>

Bohr Model

• atoms are electrically neutral
• two different models can be used to describe electron configuration

1.   Energy Level Model
2.   Bohr Model

• electrons occupy shells which are divided into orbitals
• 2 e´ in the first orbital
• 8 e´ in the second orbital  --->
• 8 e´ in the third orbital     --->      Octet

Sulphur (S):

• protons: 16
• neutrons: 16
• electrons: 16
• energy level model:

              6 e´
              8 e´
              2 e´

• bohr model:

   Sodium (Na):

• protons: 11
• neutrons: 12
• electrons: 11
• energy level model:

               1 e´
               8 e´
               2 e´

• bohr model:

   -Eva           
                      

Bohr diagrams

-Bohr model

-Bohr diagram periodic table

• examples:

Carbon (C):

• atomic number-number of protones: 6
• atomic mass-number of protones and neutrones: 12
• neutrons: 12-6--> 6

Lithium (Li):

• atomic number: 3
• atomic mass: 7
• neutrons: 7-3-->4

-Eva

Atomic Theories Continued

Bohr (1920s)
I. Rutherford's model was unstable
     A. Protons and electrons should attract each other
II. Matter emits light when it is heated
III. Light travels as photons
     A. The energy photons carry depends on their wavelengths
IIII. Bohr based his model on the energy (light) emitted by different atoms
     A. Each atom has a specific spectra of light

Bohr's Theory
1. Electrons exist in orbitals
2. When they absorb the energy they move to a higher orbital
3.As they fall from a higher orbital to a lower one they release energy as a photon of light

-Nicole

Atomic Theories

Democritus:

• atoms were indivisible particles
• first mention of atoms
• problems: not testable

Lavoisier:

• law of conservation of mass
• law of define proportions

Proust:

• if a compound is broken down into its constituents the products exist in the same ratio as in the compound

Dalton:

• atoms are solid, indestructibile spheres
• provides for different elements
• based on the law of conservation of mass

Thomson:

• raisin bun model 
• solid, positive spheres with negative particles
• first atomic theory to have positive and negative charges

Rutheford:

• atoms have a positive, dense centre with electrons outside it
• planetary model
• explains why electrons spin around nucleous

-Eva         

Density and Graphing

DENSITY
I. Formula: density= mass/ volume
    A. Density is usually expressed in kg/L, kg/m³, or g/cm³

Ex. Determine the density of a statue that has a mass of 135 kg and a volume of 65 L.
     d= mass/ volume
     d= 135 kg/ 65 L
     d= 2.1 kg/ L


GRAPHING
I. All graphs must have:
     A. Labelled axis
     B. An appropriate scale
          a. Every interval should be equal
     C. Title
     D. Data points
     E. Line of best fit
          a. A smooth line

II. 3 tools you have when looking at a graph:
     A. Read the information on the graph
     B. Calculate the slope of the graph
     C. Calculate the area of the graph

Ex.



1a) Find the slope between 12:00 pm - 3:00 pm.

Slope= rise/ run
Slope= 6/ 3

Slope= 2°C/ hr

1b) What does the slope represent?

The slope reprsents the increase of temperature per hour.

2) Find the total area from 12:00 pm to 6:00 pm.

How to:
1. Split the graph up into triangles and rectangles.
2. Find the area for each individual shape.
     A. Formula for finding the area for triangles: area= (base x height) / (2)
     B. Formula for finding the erea for rectangles: area= (length x width)
3. Add all the areas together to find the TOTAL AREA.

Section A = area inbetween 12:00 pm and 3:00 pm. (Triangle)
area= (base x height) / (2)
area= (3 x 6) / (2)
area= 9°C·hr

Section B = area inbetween 3:00 pm and 5:00 pm. (Rectangle)
area= (length x width)
area= (2 x 6)
area= 12 °C·hr

Section C = area inbetween 5:00 pm and 6:00 pm that is above
26°C. (Triangle)
area= (base x height) / (2)
area= (1 x 5) / (2)
area= 2.5 °C·hr

Section D= area inbetween 5:00 pm and 6:00 pm that is below 26°C. (Rectangle)
area= (length x width)
area= (1 x 1)
area= 1°C·hr

Total area= A+B+C+D
Total area= 9+12+2.5+1
Total area= 24.5 °C·hr

-Nicole!!!!!