1. Small Molecules: Structure and Behavior

2. Atoms: The Constituents of Matter
Matter is composed of atoms with positively charged nuclei of protons and neutrons surrounded by negatively charged electrons.

3. Classification of Elements

4. Main Elements Found in Living Organisms

5. Isotopes of an element differ in numbers of neutrons
Some isotopes are unstable and are termed radioactive. These radioisotopes are useful for many purposes.

6. Electrons are distributed in orbitals
Each orbital contains a max of 2 electrons

7. Orbital Shell Representations

8. Bonding Occurs Due to Electrons

9. Ionic bonds Complete gain/loss of electron to form a charged species
Oppositely charged ions then interact electrostatically

10. Covalent Bonds 2 nuclei share one or more pairs of electrons.
electrons in orbitals whose spatial orientations give molecules shapes

11. Covalent Bonds
Combining electrons in all the orbitals into a new set of orbitals often occurs.
sp3 bonds of carbon are the combination of the 2s orbital and the 3, 2p orbitals to form 4 sp3 orbitals which each have a single electron that is shared with the single electron in H’s 1s orbital

12. Table 2.2
Table 2.2

13. Covalent Bonds Nonpolar covalent bonds Polar covalent bonds
electronegativities of two atoms are ~ equal.
electronegativity difference <1
Polar covalent bonds
Between atoms with strong electronegativity & atoms with weaker electronegativity
electronegativity difference >1

15. Polar Covalent Bonds
figure jpg

16. Polar & Non-polar Molecules
Electronegativity difference:
O 3.5, H 2.1
= 1.4
Electronegativity difference:
C 2.5, H 2.1
= 0.4

17. Polarity of H2O Dissolves Ionic Compounds

18. Hydrogen Bonds
form btwn a d+ H atom in one molc & a d– N or O atom in another molc or region of same molc.
H donated by
-O-H
-N-H
H accepted by
O= O- -O-H
:N- =N- : : : : : : :

19. Hydrogen bonds
figure jpg

20. H-Bonds in H2O

21. Van der Waals Forces
Weak molecular orbital interactions between non-polar molecules

22. Chemical Reactions:
Substances change their atomic compositions and properties.
Energy is either released or added.
Matter and energy are not created or destroyed, but change form.

23. Chemical Reactions

24. Ionization of H2O – Basis of pH

25. Acids, Bases, and the pH Scale
Substances that donate H ions
Bases
Substances that accept H ions.
The pH of a solution is a result of its [H+]
pH= -log[H+]
pH < 7 = acidic
pH > 7 = basic

26. pH and Buffers
Buffers
Systems of weak acids and bases that resist changes in pH
Common buffering compounds
Phosphate
Carbonate
Acetate
Citrate

27. The Properties of Molecules
Molecules vary in size, shape, reactivity, solubility, and other chemical properties.
Functional groups make up part of a larger molecule and have particular chemical properties.
The consistent chemical behavior of functional groups helps us understand the properties of the molecules that contain them.