1. Chemistry of Life
Chapter 2

2. Atom Element = the smallest unit of matter that cannot be broken down
= a pure substance made of only one kind of atom

3. Atoms are composed of even smaller parts, called subatomic particles.
Protons = positive electric charge (1+)
Neutrons = neutral charge (0)
Electrons = negative charge (1-)

4. Each element has a unique number of protons
= atomic number.

5. Atoms have equal numbers of P and e-
The atomic number = tells the number of protons and the number of electrons

6. Mass number = the sum of the number of protons
and neutrons in the nucleus of an atom.
# Neutrons = Mass # - Atomic #
# protons?
# electrons?
# neutrons?
Carbon =

7. YouTube - The element song

8. Atoms want to be “stable” = full valence shell.
Chemical bonds
Atoms want to be “stable” = full valence shell.
Share or transfer electrons.
To become stable, atoms will hold together by chemical bonds.
The strongest chemical bonds are covalent bonds and ionic bonds.

9. Single
Atoms
Chemical
Bond

10. A covalent bond is the sharing of a pair of electrons by two atoms.
Hydrogen H2
Subscript (2 atoms)

11. Ionic bond = one atom strips an electron completely from the other.
Ions = charged atoms or molecule
NaCl

12. Top 4 Atoms found in Organisms?
C = 18.5%
H = 9.5%
N = 3.3%

13. Properties of Water

14. Cells 70-95% Water
~75% Earth
Astronomers
Life evolved in water

15. H2O

16. - + Water is a “Polar Molecule”
Polar Covalent Bond = electrons not shared equally - +

17. Hydrogen bonds = a weak chemical attraction between polar molecules.
H+  O-

18. Cohesion = water molecules bonding to each other.
“Surface tension” prevents
stretch or break the surface

19. Adhesion = clinging of one substance to another (polar  polar).

20. Water is the “solvent” of life
Solution = homogenous mixture.
Solute =
Solvent =
substance dissolved
dissolving agent

21. Forms hydrogen bonds with charged and polar covalent molecules.
Solvent?
Solute?
“Dissolve”

22. pH

23. 0 - 14 7 = neutral (H+ = OH-) 0-6 = acidic (H+) 8-14 = basic (OH-)
pH scale = concentration of H+ in a solution
0 - 14
7 = neutral (H+ = OH-)
0-6 = acidic (H+)
8-14 = basic (OH-)

24. Acid = any compound that forms hydrogen ions (H+) ions in solution
Base = any compound that forms
hydroxide ions (OH-) in solution
Factor of 10

26. Buffers = weak acids or Cell pH = 6.5 – 7.5 “Homeostasis”
bases that prevent
sudden changes in pH