1. Chapter 6 Notes Chemical Bonding
Classic joke of the day:
Two atoms walking down the street, one atom gets bumped by another. He shouts “Hey he stole my electron”. His friend asks “Are you sure?!” to which he replies “ Yes, I’m positive”
Hey.. That’s Ionic!!!
Pre-AP Chemistry

2. Chapter 6 Vocabulary chemical bond ionic bonding covalent bond
nonpolar-covalent bond
polar-covalent bond 2

3. Section 6.1 Intro to Chemical Bonding
Main Ideas:
Atoms Form Compounds by gaining, losing, or sharing electrons.
Atoms tend to form bonds to follow the octet rule
Atoms will bond in order to lower their potential energy.
Ionic bonds form from gaining and losing electrons
Covalent bonds form from shared electrons

4. Valence Electrons are…?
The electrons responsible for the chemical properties of atoms, and are those in the outer energy level.
Valence electrons - the s and p electrons in the outer energy level
the highest occupied energy level
Core electrons – are those in the energy levels below.

5. The Octet Rule
In Chapter 5, we learned that noble gases are unreactive in chemical reactions
In 1916, Gilbert Lewis used this fact to explain why atoms form certain kinds of ions and molecules
The Octet Rule: in forming compounds, atoms tend to achieve a noble gas configuration; 8 in the outer level (s and p) is stable
Each noble gas (except He, which has 2) has 8 electrons in the outer level

6. Chemical Bond
A link between atoms that results from the mutual attraction of their nuclei for electrons
Electrostatic attraction between proton and electron
Classified by the way the valence e- are distributed around nuclei of combined atoms

7. Types of Bonds
Ionic
A chemical bond resulting from electrostatic attraction between cations and anions
In a pure ionic bond, one atom completely gives up one or more e- to another atom (rarely happens)
Illustration:
A + B A B-

8. Covalent
Chemical bond resulting from the sharing of valence electrons between two atoms
In a pure covalent the electrons are shared equally between the two atoms (called nonpolar covalent)
Most covalent result in the electrons being shared unequally between atoms (called polar covalent)

9. Covalent bonds Nonmetals hold on to their valence electrons.
They can’t give away electrons to bond.
But still want noble gas configuration.
Get it by sharing valence electrons with each other = covalent bonding
By sharing, both atoms get to count the electrons toward a noble gas configuration.

10. No bond is completely ionic and is rarely completely covalent
Bonds range between the two extremes
Degree of ionic or covalent estimated by comparing electronegativities (ionic character)

11. Ionic Bonds
Ionic - Greater the difference (≥50%), the more ionic the bond
Range of considered ionic
Example:
Cs + F
4.0 ( F electroneg.) - .7 (Cs electroneg) = 3.3 Ionic bond formed
Cs becomes cation, F becomes anion

12. Covalent bonds occur if the difference is less than 50%
A bond between 2 identical atoms is completely covalent (7 diatomics: H, N, O, F, Cl, Br, I)
Types of covalent
Nonpolar
Polar

13. Nonpolar-covalent Bonds
Pole= unequal distribution of charge
nonpolar-covalent bond- the bonding electrons are shared equally by bonded atoms, with a resulting balanced distribution of electrical charge
Occur between 0% to 5% ionic character
Range of difference 0 - ~0.3

14. Polar-covalent Bonds Polar Pole= unequal distribution of charge
Polar covalent bond is a bond where united atoms have an unequal attraction for the shared electrons
Occur between 5%-~50% ionic character
Range of difference ~

15. Examples H - H 2.1 -2.1= 0 nonpolar covalent bond H - Cl
Because Cl is more electronegative, it has a stronger attraction for the e-, thus an uneven pull of electrons occurs—however e- still shared
Uneven sharing causes a partial positive, partial negative pole

16. Metallic Bonding
In a liquid or solid state, metals readily give up electrons
When only other metal atoms are around, electrons are not accepted and held, they are free to move
Free moving electrons called an electron sea—reason for metallic properties of luster, malleability, ductility, and conductivity

17. Why do atoms bond?
Atoms will bond in order to lower their potential energy. (most atoms at high potential energy)
Atoms strive to reach an octet by bonding (ie: can take on the configuration of a noble gas)

18. Quick Trick
Polar covalent and nonpolar covalent bonding most readily occurs between
Ionic most readily occurs between
Metallic occurs between metals
nonmetals
metals and nonmetals

19. A. Chemical Bond
.. a mutual electrical attraction between nuclei and valence electrons of different atoms that binds the atoms together
Two types:
1. Ionic bonds – transfer of electrons (gained or lost; makes formula unit)
-usually metal-nonmetal bond
-forms cations and anions
-range of
2. Covalent bonds – sharing of electrons. The resulting particle is called a “molecule”
-usually nonmetal-nonmetal bond
a) nonpolar - range of difference 0 - ~0.3
b) polar- range of difference ~

20. Sec 6.1 Practice Problems textbook page 200 #6-7)
6. Complete chart. (Hint: See Sample A page 167)
Bonded Elements
Electronegativity
Difference
Bond Type
More Electronegative
Atom
a. H, I
b. S, O
c. K, Br
d. Si, Cl
e. K, Cl
f. Se, S
g. C, H
7. List the bonding pairs described in item 6 in order of increasing covalent character (decreasing ionic).

21. Sec 6.1 Additional Practice problems
Determine the electronegativity difference, bond type, and more electronegative element with respect to the following atoms.
H and F
Br and Br
Al and S
Na and S
At and Cl
Ba and O
Si and O
Cr and Cl
Fe and I
K and Br