Ch 8 Notes:

Section 1

Objective:  (7C) construct electron dot

formulas to illustrate ionic bonds.

What is a chemical bond?

Force of attraction (not a physical link) b/w

bonding atoms;

 

How is a positive ion formed?

By losing electrons

 

How is a negative ion formed?

By gaining electrons

 

Why do ions form? (remember Octet Rule?)

Atoms gain more stable electron

configurations by losing or gaining electrons.

 

What is an ionic bond? Electrostatic attraction

b/w + and – ions (due to the transfer of e-)

 

How is electron configuration related to

formation of a chemical bond?

e- conf. tells us whether atoms will gain/lose e-

which tells us whether they will become + or – ions;

The + and – ions are attracted (ionic bond)

 

Handout: Ch. 8 Practice (drawing Lewis diagrams, and modeling ionic bonding)

 

Helpful YouTube lessons: You can find many good you tube lessons on this subject. For example, go to you  tube and search Electron Dot Diagram” by Papapodcasts;  The lesson shows the steps to drawing Lewis structures.  Also search for “Chemistry Tutorial 5.01: Ionic Bonding” by Mark Rosengarten.  This lesson explains ionic bonding.

MgCl2    (chemical formula)

Magnesium Chloride (name)

Should be able to tell what kind of bond it is:

Ionic- metal bonded to a nonmetal;  MgCl2

Covalent-between two nonmetals; H2O

Identify the atoms & tell how many of each kind:

MgCl2

Mg-1  Cl-2

 

Ratio between the atoms

1:2 ratio of Mg to Cl

Formula Unit- simplest Ratio              MgCl2

                                    Mg2Cl4  (wrong)

Binary Compound-only two different elements (MgCl2)

Oxidation Numbers-# of valence e-‘s lost or gained & resulting charge (+ or -)

(write the oxidation #’s across the top of your PT)

Assignment: Make flash cards for Ch 8 vocab words on p. 235.

Vocabulary Quiz later this week.

Polyatomic Ion-          

(OH)-       hydroxide ion;

Ion containing more than one atom; 

Mg(OH)2  Magnesium Hydroxide

Mg-1 atom      H-2 atoms       O-2 atoms

Ø  This is not a binary compound b/c it contains >2 different elements.

Do   (MiniLab:Oxidation Blocks)

Rules for Formula Writing:

1.                  Cations are written 1st, then anions

2.                  Subscripts of 1 are understood, do not write them

3.                  Complete, correct formulas have a net charge of zero.

4.                  There are no oxidation numbers (superscripts) written as part of the chemical formula.

Naming Rules

Binary Ionic Compounds

1.                  Write the name of the cation first (no changes)

2.                  Write the root word name of the anion –

Chlor-                    Nitr-

Ox-                                    Fluor-

Sulf-                                   Phosph-

Iod-

3.                  Add the ending “-ide” to the anion name.

Example:   NaCl   

Sodium Chloride

Lesson: Writing formulas for ionic compounds that contain polyatomic ions (p.224)

Polyatomic ions- contain more than one atom, act as a single unit, with one oxidation number. See p. 224 table 8-6. 

Follow same rules as for writing the formula of binary compounds, EXCEPT- use parentheses around the polyatomic ion if the quantity is >1.  Place the appropriate subscript OUTSIDE the parentheses.  Never change the subscripts within the polyatomic ion. For example: Ca(OH)2 contains 1 calcium and 2 hydroxide ions.

Ø  Write the formula for a compound containing Aluminum and the polyatomic ion “Sulfate”.

Ø  Study p. 225 Example Problem & do Practice problems # 24-28.

Lesson: Naming compounds that contain polyatomic ions (p.225-227)

Naming Rules 

1.                  Write the name of the cation first (no changes)

2.                  Write the name of the polyatomic anion –

Example:               NaOH   Sodium Hydroxide

                              KCLO3        Potassium Chlorate

Ø  P. 226 practice problems #31 & 33.

Lesson: Writing formulas for compounds that contain transition metals (multivalent metals) (p.226)

p.213 “It is difficult to predict the number of electrons lost by transition elements.” Also metals in groups 3A & 4A are unpredictable.  See p. 222 table 8-5.  Use it as a reference for possible charges for these metals. 

Copper Cu+ (known as “copper I”)and Cu2+(known as “copper II”) form different compounds with the same anion because the ratio must be different in order to produce a net charge of zero on the resulting ionic compound:              CuCl  and CuCl2 respectively.

Ø  Write formulas for all of the ionic compounds that can be formed between Iron (Fe2+ and Fe3+) and Oxygen.

Ø  Practice Problems: Write formulas & names for the following: all oxidation states of Gold (2) and Cobalt (2) with sulfite, nitrite, and phosphorus=12 formulas

Answers:   Gold (+1, +3)                      Cobalt (+2, +3)

Ø  Sulfite (SO3 2-), nitrite(NO2 1-), and phosphorus(P 3-),

                                               

 

SO3 2-

NO2 1-

P 3-

Au+1

Au2SO3

AuNO2

Au3P

Au+3

Au2(SO3)3

Au(NO2)3

AuP

Co+2

CoSO3

Co(NO2)2

Co3P2

Co+3

Co2(SO3)3

Co(NO2)3

CoP

           

Lesson: Naming  compounds that contain transition metals (multivalent metals) (p.226)

1.                  Write the name of the cation first, but  in order to differentiate between Cu+ (known as “copper I”)and Cu2+(known as “copper II”), the oxidation number is written as a roman numeral in parentheses after the name of the cation.  For example,  Copper (I)

2.                  a) If the anion in monoatomic, write the root word name of the anion – and add the “-ide” ending. For example,  Copper (I) Chloride is the name of CuCl. 

b) If the anion is polyatomic, simple write the name of the polyatomic ion.

For example,  Copper (I) Nitrate is the name of CuNO3. 

Ø  P. 226 practice problems #32 & 33.

Assignment: P. 227 Question # 39-copy in table format.  You must also NAME the resulting compounds.

This website has power points and notes about formula writing and naming (see Unit one , lessons 12-14) 

http://www.chalkbored.com/lessons/chemistry-11.htm

There are MANY other websites, just google search the terms above