1. Chapter 2 The Chemical Context of Life

2. Comment
Much of this chapter should be review from a basic chemistry course.

4. Matter

5. Atoms

6. Element

7. Compound

8. Question? What Elements are necessary For Life?
Life requires about 25 chemical elements.

10. Macroelements

11. Control
Minus Nitrogen

12. Microelements

13. Goiter – minus Iodine

14. Atomic Number

15. Atomic Mass

16. Atomic Model

17. Isotopes

18. Types of Isotopes
Radioactive
2. Heavy -

20. Energy

21. Potential Energy
Is the energy that matter stores because of its position or location.
Electrons have potential energy because of their position relative to the nucleus.

23. Electron Energy Levels

24. Electron Orbitals .

25. Electron Orbitals

26. Chemical Behavior Of An Atom
Is determined by its electron configuration in the energy levels and orbitals.

27. Valence Electrons

28. Octet Rule

29. Electrons of the first elements

30. Chemical Bonds

31. Bond Formation Depends On:
The number of valence electrons that must be gained, lost, or shared to reach the stable condition.

32. Chemical Bond Types

33. When electrons are shared equally between atoms.
Very strong bond.
Important in many molecules found in living things Ex: carbon to hydrogen

34. Can be single, double, or triple between two atoms.
Each nonpolar covalent bond involves a pair of electrons.

36. When electrons are shared unequally between atoms.
Results in “polar” molecules that have charged areas. Ex: Water, H to O bonds

37. Formed when electrons are transferred from one atom to another and ions are formed.

38. Types of Ions
Cations –
Anions –

39. Formed when cations and anions attract each other.
Weak chemical bond.

40. Ionic Bonds

42. When a hydrogen atom bonded to one molecule is attracted to the slightly negative area (often N or O) of another molecule.
Very weak individual bond.
Can be a “strong” force if there are many H bonds.

43. Hydrogen Bonds

44. Molecular Shape

46. Chemical Reactions

47. Parts of the Equation 2 H2 + O2 2 H2O Reactants: Products:
Note - all atoms of the reactants must be accounted for in the products.

48. Chemical Equilibrium
Ex:
3 H2 + N NH3

49. Summary Element vs compound Macro and micro elements
Atomic Number and Mass
Isotopes
Valence electrons
Chemical Bonds

50. Summary
We will now put elements together to form molecules and build the next level in the hierarchy.