ATOMS and BONDS

1
ATOMS and BONDS

• Review for Lecture P021

2
ELECTRONS -- the most important concept in this
chapter

• All biological energy involves transfer of
  electrons from one position to another, and
• all the characteristics of biological molecules
  can be traced to the position of electrons.
• Electrons connect atoms into molecules.    

3
Important details 

• What are the parts of an atom, and how are they
  connected to isotopes and to radiometric dating?
• Bonds compare and contrast three types. How
  are bonds connected to polarity and solubility?
• chemical reactions and energy how are they
  related?
• How are electrons involved in energy, molecule
  formation, polarity?

4
(No Transcript)
5
What are the parts of an atom, and how are they
connected to isotopes and to radiometric dating?

• Study pp. 19-21 carefully
• which particles are in the nucleus?
• which particle has a negative charge?
• In an uncharged atom, the number of protons is
  the same as the number of ______.
• Which particle has the smallest mass?
• Which particle changes position in ordinary
  chemical reactions?
• Life as we know it depends on changes of position
  of which particle?

6
ELECTRONS

• Travel at the speed of light
• sometimes act like particles and have a small
  mass
• sometimes act like waves and have a wavelength of
  10-12 meters
• find other electrons repelling/repulsive
• are attracted to protons, but are moving too fast
  to leave their orbitals (like the moon)
• when they lose energy, they move closer to
  protons. Gaining energy moves them out and makes
  them likely to stray from the unstable and
  disfunctional relationship.

7
(No Transcript)
8
What are the parts of an atom, and how are they
connected to isotopes and to radiometric dating?

• Study pp. 19-21 carefully
• Two isotopes of the same element have different
  numbers of ______.
• Therefore, the two isotopes of the same element
  will differ in m _ _ _ and sometimes in r_ _ _ _
  _ _ _ ....
• How can the proportion or ratio of the two
  isotopes can be estimated?
• How can you estimate the age of a fossil or
  residue?

9
(No Transcript)
10
Bonds compare and contrast three
types.

• Covalent pp. 22-23
• hydrogen p. 32
• ionic pp. 33, 35d-37

11
(No Transcript)
12
Figure 2.6a-c
13

• Electrons in
• C-H
• bonds are
• evenly shared
• C-H regions
• are nonpolar

14
But electrons are not shared evenly in O - H
bonds. O - H bonds gt polar
15
Hydrogen bonds are like static electricity--
weak attractions of opposites

• Uneven sharing of electrons causes polar areas of
  molecules
• Polar areas have slight negative charges if the
  electrons are attracted more strongly to them
• Slight positive charges are in the areas with
  weaker attraction for the electrons.
• The negative areas are attracted to positive
  areas of other molecules or other parts of very
  large molecules

16
Figure 2.15a,b
d-
Water is polar.
O
H
H
d
d
Hydrogen bonds form between water molecules.
d
d-
17
Figure 2.18a-d
Table salt is a crystal composed of two ions.
A chloride ion being formed
Gain ofelectron
Cl-
Cl-
Cl
Cl
Cl
Na
Anionformation
Ionic solids dissolve readily in water.
d
d-
d-
Na
d
Cl-
Cl
d
d-
A sodium ion being formed
d
Loss ofelectron
Na
Na
Cation formation
18
Bonds compare and contrast three
types.

• Covalent pp. 22-23
• hydrogen p. 32
• ionic pp. 33, 35d-37

19
4th force, not in your textbook van der Waals

• All atoms and molecules are attracted to each
  other when theyre about 3.5 x 10-10 m apart
  (about a million times smaller than what you can
  see)

20
Bonds How are bonds connected to polarity and
solubility?

• See box 2.2 p. 36

21
Figure 2.18d
Ionic solids dissolve readily in water.
d
d-
d-
d
Cl-
Na
d
d-
d
22

• Hydophobic
• nonpolar
• Hydrophilic
• gt polar
• ionic or
• hydrogen bonds

23

• Electrons in
• C-H
• bonds are
• evenly shared
• C-H regions
• are nonpolar

24
But electrons are not shared evenly in O - H
bonds. O - H bonds gt polar
25
chemical reactions and energy how are they
related?

• Activity 2.1!
• Pp. 25 ff.
• Fig. 2.9
• fig. 2.12

26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
chemical reactions and energy how are they
related?

• Reduction is the gain of electrons (and potential
  energy)
• Oxidation is the loss of electrons (and potential
  energy). Oxidation does not necessarily involve
  oxygen.

30
(No Transcript)
31
How are electrons involved in energy,
molecule formation, polarity?

• Review points and quiz questions.

32
TYPES of BONDS

• What holds atoms together in a covalent bond?
• What holds atoms together in an ionic bond?
• What kinds of forces hold separate molecules
  together?

33
The laws of chemistry change.http//www.sciencem
ag.org/content/vol283/issue5401/images/large/472-1
-large.jpg

34
http//www.sciencemag.org/cgi/content/full/300/562
0/745/F1
35
(No Transcript)
36
Chapter 2
Electrons!