1. Do Now:
What are valence electrons?
give a definition
give an example

2. Chemical Bonds DO NOW: What makes up an ionic compound?
Describe what happens to the electrons in an ionic bond.

3. Describe what happens to the electrons in an ionic bond.
What makes up an ionic compound?
A metal and a nonmetal (cation and anion)
Describe what happens to the electrons in an ionic bond.
The electrons are given away by the cation and taken by the anion
There is NO sharing of the electrons

4. Electronegativity
Electronegativity is a measure of an atom’s attraction for another atom’s electrons.
Is directly related to Electron Affinity
scale that ranges from 0 to 4.
Fluorine is the most electronegative

5. Electron Affinity Electron affinity = “Love” of electrons
Energy change accompanying addition of electron to gaseous atom:
Cl + e−  Cl−

6. Electron Affinity & Electronegativity
INCREASES
INCREASES 1A 8A H
2.1 B
2.0 P As Se
2.4 Ru
2.2 Rh Pd Te Os Ir Pt Au Po At ` 1 1 2A 3A 4A 5A 6A 7A Li
1.0 Be
1.5 Al Si
1.8 Ti V
1.6 Cr Mn Fe Co Ni Cu
1.9 Zn
1.7 Ga Ge Nb Mo Tc Ag Cd In Sn Sb Ta W Re Hg Tl Pb Bi N
3.0 O
3.5 F
4.0 Cl C
2.5 S Br
2.8 I 2 2 Na
0.9 K
0.8 Rb Cs
0.7 Ba Fr Ra
Below 1.0 Mg
1.2 3 3 3B 4B 5B 6B 7B 1B 2B
Period Ca
1.0 Sc
1.3 4 4 Sr
1.0 Y
1.2 Zr
1.4 5 5
Linus Pauling ( ) awarded Nobel Prize in chemistry in 1954 for his text, The Nature of the Chemical Bond,
and also won the Nobel Peace Prize in for his fight to control nuclear weapons.
The greater the electronegativity of an atom in a molecule, the more strongly it attracts the electrons in a covalent bond. La
1.1  Hf
1.3 6 6 Ac
1.1   7
Electronegativity 
Lanthanides:
Actinides:
Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 373

7. Which element in each pair has a higher electronegativity value?
Cl or F
C or N
Mg or Ne
As or Ca

8. Copy This in to Your Notes

9. Bonding Atoms Why do atoms bond?
each atom wants a full outermost energy level
gain, lose, and share valence electrons to achieve the duet or octet rule
gives each atom an electron configuration isoelectronic to that of a noble gas

10. Chemical Bonds Chemical Bonds
attractive force that holds atoms or ions together
3 types: ionic, covalent, metallic
- determines the structure of compound
- structure affects properties
- melting/boiling pts, conductivity etc.

11. IONIC BOND bond formed between two ions by the transfer of electrons

12. Formation of Ions from Metals
Ionic compounds result when metals react with nonmetals
Bond formed by transfer of electrons
Examples; NaCl, CaCl2, K2O

14. Ionic Bonds: One Big Greedy Thief Dog!

15. IONIC compound Mini-Review:
Made of metal cations and nonmetal anions
Held together with ionic bonds
High MP and BP
Crystalline solids at room temperature
Brittle
Conduct electricity when dissolved in water

17. COVALENT BOND bond formed by the sharing of electrons

18. Covalent Bond
Between nonmetallic elements of similar electronegativity.
Formed by sharing electron pairs
Examples; O2, CO2, C2H6, H2O, SiC

19. A chemical bond in which 2 atoms share electrons.
Covalent bonds form between 2 or more nonmetals
Both atoms attract the 2 shared electrons at the same time.

20. Properties of Covalent Compounds
Lower melting points and boiling points when compared to ionic compounds
Most do NOT dissolve in water
DO NOT conduct electricity when dissolved in water (again most do not dissolve). This is because they are not made of ions!
Form molecules vs. formula units
Solid, liquid, or gas at room temp

21. Covalent Bonds

22. Bonds in all the polyatomic ions and diatomics are all covalent bonds

23. when electrons are shared equally
NONPOLAR COVALENT BONDS
when electrons are shared equally
H2 or Cl2

24. HONClBrIF Diatomic Molecules
Molecules made up of two of the same types of atoms.
There are 7 diatomic molecules.
H2, N2, O2, F2, Cl2, Br2, I2
HONClBrIF

25. Hydrogen The hydrogen molecule has a single covalent bond.
Shared electron pair
H· ·H  H:H hydrogen hydrogen hydrogen
Atom Atom molecule
The hydrogen molecule has a single covalent bond.
The electronegativity of each hydrogen atom is the same, so the electrons are equally shared.

26. when electrons are shared but shared unequally
POLAR COVALENT BONDS
when electrons are shared but shared unequally
H2O

27. Polar Covalent Bonds: Unevenly matched, but willing to share.

28. water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

29. What types of bonds are present?
BaI2
P4S3
Ca(OH)2
FeCO3
B2Cl4
Na2Cr2O7
I2O5
Cu(ClO4)2
CS2