1. Chemical Bonds
Power Point 12
Image Credit: Khan Academy

2. Student Learning Objectives
Describe and predict types of chemical bonds
Determine the type of chemical bond
Write the chemical formula
Describe molecular attractions & provide examples
Image: Wikimedia Commons

3. Video by Kosasihiskansarsjah
Video by Kosasihiskansarsjah

4. A chemical bond is an attraction between atoms.
What is a chemical bond?
A chemical bond is an attraction between atoms.
The chemical bond puts each atom in a lower energy state.
Ibuprofen C13H18O2
Images: NASA & Wikimedia Commons

5. What is conserved in chemical reactions?
Mass and charge are conserved in chemical reactions.
The formula mass of the product is equal to the formula mass of the reactants.
The relative mass for a molecule follows the law of definite proportions.
Specific ratios of atoms
H2O

6. Practice
Apply the conservation of mass and law of definite proportions to these molecules.
Calculate the formula mass.
Set up the ratio and determine the relative mass.
State the chemical and common name.
CO HCl NH CH4

7. Lewis Dot Symbols
The Lewis electron dot symbols represent the valence electrons of the main group elements.
Unpaired e–
The electron dot structure is based on the octet rule.

8. Practice H C Ar Na Draw the electron dot structures.
How do the dot structures compare to the group number?

9. Dot Structures & Group Numbers
Image: texas.gateway.org

10. Na + Cl Be + N What is an ionic bond?
Ionic bonds form between positive and negative ions.
Electric force establishes bond
Strongest chemical bond
Ion charges must balance to a net charge of zero when atoms bond.
Na + Cl Be + N

11. Practice Mg + S Ca + Br Rb + Se
Ionic bonds are usually formed between metals from the left side of the periodic table and nonmetals from the far right side of the periodic table. Why?
Determine the chemical formula, and then name the compound.
Mg + S Ca + Br Rb + Se

12. What is a metallic bond?
Metallic bonds form between metals as all electrons are shared among all the nuclei in the metal alloy.
e e e
e e e e e
e e e
e e e e e
Sharing of all electrons establishes bond
Results in conductivity and malleability of metal materials
Ions are homogeneously distributed in alloys
Weakest chemical bond Cu Cu Ni Ni

13. What is a covalent bond?
Covalent bonds are formed between atoms that share pairs of electrons in the inter-nuclear region.
Image: Wikimedia Commons

14. Covalent Sharing of e—
Sharing of electron pairs establishes the covalent bond.
There can be 1, 2, or 3 pairs of electrons shared.
H – H e single bond
C  O e double bond
N  N e triple bond

15. Polar Molecules
In general, the more left/right separation on the periodic table, the more polar the bond will be.
Polar molecules are not symmetric.
Uneven sharing of electrons
A-symmetric structure
socratic.org

16. Practice
Which are polar molecules? Which bond would be the most polar?
CO CO H2O NH3
Polar molecules tend to have high boiling points. Explain why the structure of an atom would cause high boiling point (high energy to phase change).

17. Molecular Attractions
Molecular attractions occur as a result of polarity.
Ion-Dipole
Ionic bonds dissolve easily in water – ions
Ionic substances are very hydrophilic (water-loving)
Potassium Chloride solute
Water solvent
Image Credit: Chemistry Libretexts

18. Dipole-Induced dipole
Dipole-Dipole
Water molecules are dipoles
Intermolecular forces attract water molecules together
Dipole-Induced dipole
CO2 vibrates and becomes polar
The polar CO2 attracts to water dipoles
Soda Pop
(Water-Carbon Dioxide)
Images: Openstax & ThomasNet News

19. Images: ThomasNet News
Induced Dipole-Induced Dipole
Instantaneous uneven distribution of e−
Caused by vibration of molecules
One temporary dipole induces dipole behavior in neighboring molecule
Images: ThomasNet News

20. Practice
Which of the molecular attractions is the strongest? Explain what makes these attractions strong.
Which of the molecular attractions is the weakest? Explain what makes these attractions weak.

21. Hydrogen Bonding
Hydrogen bonding is a special form of a dipole-dipole molecular attraction.
H is part of the bond pair
Uneven sharing of e− results in stronger attractions

22. Hydrogen bonding does not just occur in water.
Hydrogen bonding occurs whenever H is part of an asymmetric structure or uneven proton distribution

23. Practice
Explain why the surface tension for water tends to be much greater than other fluids.
Which following molecule(s) would exhibit hydrogen bonding? Why?
NH3 CH4 HCl BF3