1. Chapter 2: Basic Chemistry (Outline)
Chemical elements
Atoms
Isotopes
Molecules and compounds
Covalent and ionic bonding/reactions
Ionic and Covalent
Hydrogen
Properties of Water
Define/describe acids and bases
pH scale and buffers

2. Chemical Elements
Matter refers to anything that has mass and occupies space
Only 92 naturally occurring fundamental types of matter – 92 Elements
Organisms composed primarily (98%) of only six elements
Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus and Sulfur
CHNOPS

3. Elements Composition of Earth’s Crust vs. Organisms

4. Atomic Structure Atoms - smallest particles of elements
Atoms composed of 3 types of subatomic particles
Protons: positively charged particles within the nucleus
Neutrons: electrically neutral charged particles also found in nucleus
Electrons: negatively charged particles orbiting the nucleus

5. Atomic Symbol
Each element represented by unique atomic symbol
One or two letters
First letter capitalized
Superscripted number before:
Represents mass number
Number of protons & neutrons in nucleus
Subscripted number before:
Represents atomic number
Number of protons in nucleus
Mass Number
Atomic Number
Atomic Symbol 12 6
Carbon C

6. Periodic table I II III IV V VI VII VIII
Elements grouped in periodic table based on characteristics
Vertical columns = groups; chemically similar
Horizontal rows = periods; larger and larger 1 H
1.008 3 Li
6.941 11 Na
22.99 19 K
39.10 4 Be
9.012 12 Mg
24.31 20 Ca
40.08 5 B
10.81 13 Al
26.98 21 Ga
69.72 6 C
12.01 14 Si
28.09 22 Ge
72.59 7 N
14.01 15 P
30.97 23 As
74.92 8 O
16.00 16 S
32.07 24 Se
78.96 9 F
19.00 17 Cl
35.45 25 Br
79.90 10 Ne
20.18 18 Ar
39.95 26 Kr
83.60 2 He
4.003 I II
III IV V VI
VII
VIII
Groups
Periods

7. Isotopes
Isotopes: Atoms of the same element that differ in the number of neutrons. Isotopes of an element have the same chemical properties but different weights
Example: 12 6
Carbon 12 C 13
Carbon 13 14
Carbon 14

8. Electron Shells, Orbitals and Energy Levels
Atoms normally have as many electrons as protons
Opposite charges balance leaving atom neutral
Electrons are attracted to the positive nucleus
Revolve around nucleus in orbitals
Can be pushed into higher orbitals with energy
Release that energy when they fall back to lower orbital
Different energy levels referred to as electron shells

9. The Octet Rule for Distribution of Electrons
Bohr models show electron shells as concentric circles around nucleus
Each shell has two or more electron orbitals
Innermost shell has 2 orbitals
Others have 8 or multiples thereof
Atoms with fewer than 8 electrons in outermost shell are chemically reactive
If 3 or less – Tendency is to donate electrons
If 5 or more – Tendency is to receive electrons

11. Periodic Table

12. Elements and Compounds
Molecule - two or more atoms react or bond together
If all atoms in molecule are of the same element
Material is still an element
O2, H2, N2, etc.
If at least one atom is from a different element
Material formed is a compound
CO2, H2O, C6H12O6, etc.
Characteristics of compounds dramatically different from constituent elements

13. Chemical Bonding
Bonds between atoms are caused by electrons in outermost shells
The process of bond formation is called a reaction
The intensity of simple reactions can be predicted by the periodic table
If two elements are horizontally close in the table, they usually react mildly
If they are horizontally far apart, they usually react vigorously

14. Types of Bonds: Ionic Bonding
Octet rule
Atoms need 8 electrons in outer shell
If have < 4 outers, desire to donate them
If have > 4 outers, desire to receive more
Consider two elements from opposite ends of periodic table
Element from right side:
Has 7 electrons in outer shell
“Desperately needs” one more (7+1=8)
Element from left side:
Has only 1 electron in outer shell
“Desperately needs” to donate it (1-1=0=8)

15. Formation of Sodium Chloride

16. Types of Bonds: Covalent Bonds
When atoms are horizontally closer together in the periodic table
The electrons are not permanently transferred from one atom to the other like in NaCl
A pair of electrons from the outer shell will “time share” with one atom and then the other
This also causes the atoms to remain together
Known as covalent bonding

17. Covalently Bonded Molecules
Sometimes two pairs of electrons are shared between atoms – a double covalent bond (e.g. O2 )
Three pairs of electrons – a triple bond (e.g. N2)

18. Covalently Bonded Molecules

19. Nonpolar Covalent Bonds
Consider two elements that are equidistant from the edges of the periodic table
Atoms will have about equal affinity for electrons
One will “want” to donate electron(s)
The other will “want” to receive electron(s)
When bonded covalently:
The bond electrons will spend about equal time with both atoms
Such covalent bonds are said to be nonpolar

20. Polar Covalent Bonds
Some atoms attract electrons more strongly than others - electronegativity
Atoms will have unequal affinity for electrons
When bonded covalently:
The bond electrons will spend more time with one atom than the other
The atom that gets the most time with the electrons will be slightly negative
The other will be slightly positive
Such covalent bonds are said to be polar

21. Types of Bonds: Hydrogen Bonds
Water (H2O or H–O–H) is a polar molecule
Electrons spend more time with the larger oxygen atom than the smaller hydrogen atom
H becomes slightly positive and O slightly negative
When polar molecules are dissolved in water
The H of water molecules are attracted to the negative parts of the solute molecules
Results in a weak bond – the hydrogen bond
Easily broken, but many together can be quite strong
One of the most important interactions in biological molecules (e.g. proteins, DNA, etc.)

22. Water Molecule and Hydrogen Bonding

23. The Chemistry of Water: Heat Capacity
Water has a high heat capacity
Temperature = rate of vibration of molecules
When water is heated
Hydrogen bonds restrain bouncing
Temperature rises more slowly per unit heat
Thermal inertia – resistance to temperature change
Because of hydrogen bonding – takes a large heat loss or gain for each 1C change in temperature.
Hydrogen bonds must absorb heat to break, and they release heat when they form
Keeps temperature fluctuations within a range suitable for life

24. Properties of Water: Heat of Vaporization
Water has a high heat of vaporization - the energy required to convert 1g of liquid water to a gas
To raise water from 99 to 100 ºC; ~1 calorie
To raise water from 100 to 101 ºC; ~540 calories!
Large numbers of hydrogen bonds must be broken to evaporate water
This is why sweating (and panting) cools
Evaporative cooling is best when humidity is low because evaporation occurs rapidly
Great example is when you get out of the shower!

25. Properties of Water: Heat of Fusion
Heat of fusion (melting)
To raise water from -1 to 0 ºC; ~1 calorie
To raise water from 0 to 1 ºC; ~80 calories!
This is why ice at 0 ºC keeps stuff cold MUCH longer than water at 1 ºC
This is why ice is used for cooling
NOT because ice is cold
But because it absorbs so much heat before it will warm by one degree

26. Heat Content of Water at Various Temperatures

27. Properties of Water: Water as a Solvent
Solution - liquid that is a completely homogenous mixture of two or more substances
Solvent - dissolving agent of a solution
Solute - substance dissolved in a solution
Hydrophilic
Water loving, property of having an affinity for H2O
Ionic and polar compounds
Hydrophobic
Water fearing, not water-soluble
Nonpolar compounds

28. Ionic compounds dissociate in water

29. Properties of Water: Cohesion & Adhesion
Cohesion – Hydrogen bonds hold water molecules tightly together
Adhesion – Hydrogen bonds for between water and other polar materials
High Surface Tension
A measure of how difficult it is to stretch or break the surface of a liquid
Allows small nonpolar objects (like water strider) to sit on top of water

30. Water as a Transport Medium
Cohesion & adhesion are both important because combined together they form an event called capillary action
Capillary action defies gravity and helps move water up the plant to its leaves

31. Properties of Water: Uniqueness of Ice
Frozen water is less dense than liquid water
The density of water:
Prevents water from freezing from the bottom up
Ice forms on the surface first – the freezing of the water releases heat to the water below creating insulation
Makes transition between season less abrupt

32. pH of Water: Acids Acids
Dissociate in water and release hydrogen ions [H+]
Sour to taste DO NOT TASTE ACIDS IN THE LAB!!
Turn litmus red
Hydrochloric acid (stomach acid) is an inorganic acid with symbol HCl
In water, it dissociates into H+ and Cl-
Dissociation of HCl is almost total, therefore it is a strong acid

33. pH of Water: Bases Bases:
Either take up hydrogen ions [H+] or release hydroxide ions [OH-]
Feel soapy or slippery
Turn litmus blue
Bitter to taste DO NOT TASTE BASES IN THE LAB!
Sodium hydroxide is a solid with symbol NaOH
In water, it dissociates into Na and OH-
Dissociation of NaOH is almost total, therefore it is a strong base

34. pH Scale
pH scale used to indicate acidity and alkalinity of a solution
Values range from 0-14
Acidic: if pH is less than 7
Basic: if pH is greater than 7
Nuetral: is pH is equal to 7
Logarithmic Scale
Each unit change in pH represents a change of 10 times
pH of 4 is 10 times as acidic as pH of 5
pH of 10 is 100 times more basic than pH of 8

35. The pH Scale Increasing pH means the H+ ions are decreasing
Decreasing pH means H+ ions are increasing

36. Buffers and pH
When H+ is added to pure water at pH 7, pH goes down and water becomes acidic
When OH- is added to pure water at pH 7, pH goes up and water becomes alkaline
Buffers are solutes in water that resist change in pH
When H+ is added, buffer may absorb, or counter by adding OH-
When OH- is added, buffer may absorb, or counter by adding H+

37. Buffers in Nature Biological buffer system
Human blood normally 7.4 (slightly alkaline)
Many foods and metabolic processes add or subtract [H+] or [OH-]
Reducing blood pH to 7.0 results in acidosis
Increasing blood pH to 7.8 results in alkalosis
Both life threatening situations
Bicarbonate ion [-HCO3] in blood buffers pH to 7.4