october 15 th 2009 n.
Skip this Video
Download Presentation
October 15 th 2009

Loading in 2 Seconds...

play fullscreen
1 / 33

October 15 th 2009 - PowerPoint PPT Presentation

  • Uploaded on

October 15 th 2009. Objectives SWBAT Identify oxidation numbers for given ions SWBAT State the definition of electronegativity SWBAT explain electronegativity trends on the periodic table Catalyst

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'October 15 th 2009' - tiger

Download Now An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
october 15 th 2009
October 15th 2009


  • SWBAT Identify oxidation numbers for given ions
  • SWBAT State the definition of electronegativity
  • SWBAT explain electronegativity trends on the periodic table


  • Write down the stable ion that will form for the following elements: Be able to explain why…
    • Na, Ar, O, Mg
  • Label the ions above as cations or anions
catalyst review
Catalyst Review
  • Na+1, because sodium needs to lose 1e- to be stable
  • Ar, because Argon is already stable, it does not lose or gain any e-.
  • O2-, because Oxygen needs to gain 2e- to be happy
  • Mg2+, because magnesium needs to lose two electrons to be happy
  • Catalyst Review (15min)
  • Welcome to Unit 4 (5min)
  • Compounds and Chemical Bonds (10min)
  • Oxidation numbers (5min)
  • Electronegativity (20min)
  • Practice (25min)
  • Exit Ticket (10min)
new word
New word
  • Oxidation Number – the positive or negative charge on an ion
    • What is the oxidation number of Sodium?
    • Argon?
  • Na+1
  • Ar
  • O2-
  • Mg2+
what to expect in unit 4
What to expect in Unit 4
  • You will learn about…
    • Compounds (ionic and covalent)
    • Chemical formulas
    • Electronegativity, ionization energy, polarity
    • Naming compounds
    • Valence electrons continued
    • Lewis structures
  • You will get to…
    • Make Ionic Personal Ads!
    • Speed Date!
what is a compound
What is a compound?
  • A compound is a pure substance
  • A compound is a combination of two or more different elements that are chemically combined

Water molecules

Add to Vocabulary Log!

Grain Alcohol



Cane sugar



Stomach acid

Hydrochloric acid


what is a compound1
What is a compound?
  • Remember! Electrons do all the work in chemical bonds!
  • Atoms do 3 things with electrons:
    • Give them away
    • Take them
    • Share them
  • A compound is a pure substance
  • A compound is a combination of two or more different elements that are chemically combined
what is a chemical bond
What is a chemical bond?
  • A chemical bond is the force that holds two atoms together in a compound (attractive force)
  • There are two main types of bonds:
    • Ionic
    • Covalent
chemical bond spotlight nacl table salt
Chemical Bond Spotlight: NaCl (table salt)

2 different elements:

  • Sodium (Na)
  • Chlorine (Cl)

1 compound:

  • Sodium chloride (NaCl)




chemical formula
A chemical formula is a combination of chemical symbols used to represent a compound.

A chemical formula contains the number of each atom in the compound.

Chemical Formula
ratio examples
Ratio Examples
  • KBr has 1 atom of K and 1 atom of Br
  • H2O has 2 atoms of H and 1 atom of O
  • CO2 has 1 atom of C and two atoms of O
subscript numbers
Subscript Numbers
  • Subscript numbers are small numbers placed to the lower right of element symbols and are used to show how many atoms of each element are present



chemical formulas
Chemical Formulas
  • What is a chemical formula?
  • What is a subscript number?
  • What does the subscript number tell us?

If there is no number, it is an implied ONE

  • Example: Na2CO3
    • 2 atoms Na (sodium)
    • 1 atom C (carbon)
    • 3 atoms O (oxygen)
    • 6 total atoms (2 + 1 + 3 = 6)


2 Na : 1 C : 3 O

chemical formula practice
Chemical Formula Practice
  • Determine the number of each atom in the following compounds.
    • N2
    • CO
    • H2CO3
    • KOH
    • CaCO3
    • KNO3
what is electronegativity
What is electronegativity?
  • Electronegativity is…
    • The ability of an atom to attract electrons to itself in a chemical bond
    • How much an atom wants electrons
  • Electronegativity is expressed in numerical values of 4.0 or less
    • These numerical values are called Paulings
    • Higher number means the atom will attract electrons in a chemical bond

Rb has an electronegativity value of .82 Paulings

  • Br has an electronegativity value of 2.96 Paulings
    • Which one wants an electron more?
graphing electronegativity
Graphing Electronegativity
  • On two white boards in your groups:
  • Draw a line graph
    • X-axis: Element
    • Y-axis: Electronegativity
  • Part 1 – points = dots
  • Part 2 – points = squares

What trend(s) do

you notice?


Electronegativity decreases as you go down the periodic table and increases as you go left to right across the periodic table.

practice problems
Practice Problems
  • Rank the following elements in order of increasing electronegativity based on location on the periodic table (smallest to biggest)
  • Mg, Sr, Be, Ra

Radon, Strontium, Magnesium, Beryllium

Cl, Si, Al, S, P

Aluminum, Silicon, Phosphorus, Sulfur, Chlorine

let s think about the trends
Let’s Think about the Trends…
  • Discuss the following question with your group…10 class points if you come up with the right answer.
    • Why do Alkali metals have such low Electronegativities and Fluorine such a high electronegativity?
    • Why aren’t electronegativities listed for the Noble gases?
the answer
The Answer…
  • Electronegativity tells us how much an atom wants to TAKE an electron. (- charge)
  • The alkali metals have low electronegativities because in order to be stable (happy) they need to GET RID of an electron. (+ charge)
  • Halogens have a high electronegativity because in order to be stable (happy) they need to GAIN an electron (- charge)
  • Noble gases are already happy, so they do not want to gain or lose an electron (EN of zero)
how does atomic size related to electronegativity
How does atomic size related to electronegativity?

Atomic size is indirectly related to electronegativity


As electronegativity increases, atomic size decreases!


why is this relationship true
Why is this relationship true?
  • Atoms with HIGH ELECTRONEGATIVITIES hold their electrons very close!
  • Sooooo, the atomic size decreases

High or low electronegativity?

Large or small atomic size?

practice time 15min
Practice Time! (15min)
  • T or F? Electronegativity decreases as you move left across the periodic table.
  • T or F? As you move down the Periodic Table, atoms get more electronegative.
  • Rank the following sets of elements in order of increasingelectronegativity (small  big).

Set A:Bh, Mn, Re, TcSet B:Sb, I, Ag, Ru

Set C: Y, Ti, Sg, Ta

  • Rank the following sets of elements in order of decreasingelectronegativity (big  small).

Set A: Cl, At, I, F, Br Set B: Te, Xe, Sn, In

Set C:Rb, K, Sr, Ca

  • Why do Alkali metals have a lower EN then Halogens?
  • Why don’t the Noble Gases have an EN?
  • What is the relationship of atomic size to electronegativity?
  • Why does this relationship exist?
  • What are the oxidation numbers for the following elements?

A. Fluorine, Barium, Francium, Helium, Arsenic