This document summarizes key concepts in chemistry including: 1) Matter is composed of atoms which are made up of subatomic particles like protons, neutrons, and electrons. 2) Elements are substances made of only one type of atom, while compounds contain two or more elements bonded together. Water, H2O, is an example of a compound. 3) Chemical bonds like ionic bonds and covalent bonds explain how atoms combine via electron transfer or sharing. Water's properties are due to its polar covalent hydrogen bonds. 4) The pH scale measures acidity and alkalinity in solutions, and living things tightly regulate pH using buffers to maintain optimal conditions for enzyme function.

1. Chapter 2

3. Remember…..
Organism
organ system
Organs
Tissues
Cells
Molecules
atoms

4. Matter = anything that
1. has mass
2. takes up space

5. 3 Forms of Matter
Holds Shape
Fixed volume
Container shape
Free Surface
Fixed Volume
Container Shape
Volume of Container

6. Matter composed of basic substances
Elements
1. Specific chemical & physical characteristics
2. Fundamental substances
3. 1 type of atom

7. 92 naturally occurring
elements
11+ Synthetic
elements

8. Primary Elements of Living Things
1. Carbon
2. Hydrogen
3. Nitrogen
4. Oxygen
5. Phosphorus
6. Sulfur
98% 95%

9. Naming of Elements
1. Latin or English
2. Atomic Symbol =
1 or 2 letter abbreviation
Carbon = C
Hydrogen = H
Oxygen = O
Sodium = Na
Iron = Fe
Potassium = K
Nitrogen = N

11. Atom =
smallest particle of an element
that displays properties of that element

12. John Dalton: Atomic Theory
Early 1800’s
“All Matter is
composed of
atoms”

13. Structure of an Atom:
(Sub-atomical Particles)
Protons
Neutrons
Electrons

14. Sub-atomic Particles: Charges
Protons = Positive Charges
Neutrons - Neutral Charges
Nucleus
Electrons – Negative Charges

15. Atomic Number & Weight
Atomic number = number of protons
(# protons = # electrons)
Atomic weight (mass) = protons + neutrons in an atom.

16. Therefore, if…..
Atomic number = number of protons
Atomic weight = protons + neutrons
Then………
atomic weight - atomic number = # of neutrons
(P + N) (# of P) (# of N)

17. Isotopes
Isotopes = atoms of same element with:
same atomic number (# protons),
different atomic weight (# protons & neutrons)
What is different?

18. Isotopes
1. Unstable…..
• break down
2. Give off radiation
3. Used in medicine
& dating fossils

19. Electron Configuration
determines properties of an atom
• # of electrons = # of protons.
• Electron = energy in an atom
• Electrons have same weight & charge,
vary in energy content
• Farthest from nucleus =
greatest “potential energy”

20. Atomic Energy Levels
Orbital: where electrons found.
Shells: in orbitals, found in shells

21. Octet Rule
The first shell: full = 2 electrons.
Beyond first shell: full = 8 (or multiples) electrons

22. Molecule – smallest part of element or
compound that has properties of that
element or compound.
Compound - Two or more different
types of atoms that react or bond
together.

23. Chemical Formulas
1 Symbols for composition of substance.
ex: Hydrogen Cloride = HCl
2 More than 1 atom of same kind = subscript
ex: Water or H2O

24. Determining Reactivity
outer (valence) shell not full = reactive
outer (valence) shell full = not reactive
(inert)

25. outer shell = valence shell
Atoms want a full outer shell.
To complete outer shell, an atom may:
1. Give up an electron
2. Accept an electron
3. Share an electron

26. chemical bond =
transfer or sharing
electrons with another
atom

27. Electrons possess
energy
chemical bond = energy relationship

28. **Energy Relationship **
1. Energy required to form bond
2. Energy stored in chemical bonds.
3. Energy released when bond is
broken.
This concept is a top priority for living
organisms.

29. Types of Reactions
Endergonic reactions – small
molecules bonded to form large
molecules.
Energy is required.
Exergonic reactions – large molecules
broken down into small molecules.
Energy is released.

30. Chemical reactions indicated by
chemical equations
2H2 + O2  2H2O
reactants products
Equal # of atoms exist on both sides

31. Types of Reactions
• Synthesis A + B  C
• Decomposition AB  A + B
• Exchange AB + CD  AD + CB
• Reversible A + B  AB
• Oxidation loss of electron (break down)
• Reduction gain of electron (synthesis)

32. Chemical Bonds
•Ionic
•Covalent
•Polar Covalent
•Hydrogen

33. Ionic Bonding
=
transfer of electrons

34. Remember…
Atoms are electrically balanced
Electron transfer  charge imbalance
creates ions (charged atom)
ionic bond = attraction of - & +

35. 3 P +
7 P +
9 P +3 P + e-
e-e-
e- e-
e-
e-
e-
e-
e-
e-
e-

36. 3 P +
7 P +
9 P +3 P + e-
e-e-
e- e-
e-
e-
e-
e-
e-
e-
e-e-e-
3 P +
3 + and 2 –
NET = 1+
10 - and 9+
NET = 1-

37. Covalent Bonding =
sharing of electrons

38. 1. Atoms linked like a chain.
2. Very strong bonds
(single, double, etc)
3. Found in organic molecules.
(Hydrogen, Oxygen & Carbon)

39. e-
e-

40. e-
e-

41. e-
e-
e-e-
e-
e-e-
e-
e-
e-

42. e-
e-
e-
e-
e-
e-
e-
e-
e- e-

43. Polar Covalent Bonds
=
Unequal sharing
of electrons

44. • Molecule formed has both:
positive end
negative end
• “polar” molecule
• Water

48. hydrogen bond =
a slightly “+” hydrogen atom
attracted to
slightly “-”atom in other molecule

49. • Weak and easily broken
• Many together can be quite strong
• Usually the bond is with O or N
• NOT electron sharing or donating…. It is
an ATTRACTION to neighboring molecule
• Illustrated by a broken dotted line.

51. • http://programs.northlandcollege.edu/biolo
gy/Biology1111/animations/hydrogenbond
s.html

52. Chemical properties
of water
are essential to life
Living things 70–90%
water

53. Properties of Water
• Resists changes in temperature
gains and loses heat slowly
Ocean circulation = Europe’s mild winters even though it is further north than Canada.

54. Properties of Water
• Resists change in state
tends to remain liquid
high freezing point & high boiling point

55. Properties of Water
Universal Solvent
Most substances associate with water.
Facilitates chemical reactions.
solute + solvent = solution

56. Hydrophilic = “water” “loving”
(attracted to water molecules)
Hydrophobic = “water”
“fearing”
(repelled by water molecules)

57. Properties of Water
• Cohesive and Adhesive
molecules stick together & to other molecules
(effective as a transport medium)

58. Properties of Water
• High Surface Tension
Surface of water hard to break.
Basilisk Lizard

59. http://www.youtube.com/watch?v=KSLUwmJOo_M

60. Properties of Water
• Frozen water
less dense than
liquid water.
Ice (solid water)
floats on liquid
water.

61. Water has a slight tendency
to
“fall apart”
or
DISSOCIATE

62. OH- called hydroxide ion
H+ called hydrogen ion
(actually H30+)
Water dissociates into equal
numbers of:

65. Others dissociate in water
may release
unequal
amounts of “+” or “-” ions

66. Acids = produces H+ ions
taste sour
can be corrosive
Bases = can accept H+ ions
taste bitter
feel slippery

67. Acidity or Alkalinity
=
measure of relative amount of
H+ and OH- ions
dissolved in a solution

68. pH scale = indicate acidity
and basicity of a solution
Scale ranges from 0 to 14
0-3 is very acidic
7 is neutral
11-14 is very basic or alkaline

70. Control of pH
is important to organisms!!
• Enzymes function only within a narrow pH
range; usually neutral
• Buffers neutralize acids or bases in organisms
to help control pH
(by taking up or releasing H+ ions)