Atoms

1
Atoms

• Smallest electrically neutral particle of an
  element that retains the properties of that
  element.

2
Democritus

• 4th century B.C. in Greece
• Indestructible indivisible tiny particles
  called atoms

3
John Dalton

• (1766-1844) English
• Experimental evidence
• Ratios in which elements combine in chemical
  reactions

4
Daltons atomic theory

• All elements are composed of tiny indivisible
  particles called atoms.

5
Daltons atomic theory

• Atoms of the same element are identical. The
  atoms of any 1 element are different from those
  of any other element.

6
Daltons atomic theory

• Atoms of different elements can physically mix
  together or can chemically combine w/ one another
  in simple whole- number ratios to from compounds.

7
Daltons atomic theory

• Chemical reactions occur when atoms are
  separated, joined, or re-arranged. Atoms of one
  element, however, are never changed into atoms of
  another element as a result of chemical rxns.

8
Error in Daltons Atomic Theory

• atoms are divisible
• now can identify subatomic particles

9
Just How Small is an Atom

• copper atoms lined up 1 cm long 107 100 000
  000. Cu atoms
• Approximately the width of a penny.

10
Atomic Structure

• Atoms composed of e-, p, no
• Nucleus is p no

11
Electrons

• Negatively charged subatomic particles
• J.J. Thompson discovered in 1897

12
Protons

• Protons in atoms are equal to of electrons
• Have 1 charge
• Mass 1840x an electron

13
Neutrons

• Have no charge
• Same relative mass as proton

14
Atomic Number

• Atomic number is of p in nucleus of atom
• Elements different because different of protons
• p e- in atom
• H 1 p 1 e-
• O 8p 8e-

15
Periodic Table
16
Mass Number

• The sum of p no mass
• If have atomic mass of an atom of any
  element you can find composition
• Shorthand notation for composition of atom
• mass Symbol
• atomic
• 197Au
• 79

17
Isotopes

• Atoms w/ same of p but different of no
• Also has different mass

18
Isotopes

• Despite this difference they are chemically alike
• Same of p e-
• P e- are responsible for chemical behavior

19
H and C Isotopes
20
Atomic Mass Calculation

• Atomic Mass takes into account relative abundance
  of isotopes
• In nature each isotope of an element has a fixed
  mass
• In nature each isotope of an element has a
  natural abundance

21
Periodic Table
22
Atoms The Constituents of Matter

• Electrons are distributed in shells of orbitals
  containing a maximum of two. Review Figures 2.4,
  2.5

23
2.4
figure 02-04.jpg

• Figure 2.4

24
2.5
figure 02-05.jpg

• Figure 2.5

25
Atoms The Constituents of Matter

• An atom can combine with other atoms to form
  molecules. Review Table 2.1

26
2.1
27
Chemical Bonds Linking Atoms Together

• Covalent bonds form when two atomic nuclei share
  one or more pairs of electrons. They have spatial
  orientations that give molecules
  three-dimensional shapes. Review Figures 2.6,
  2.7, Table 2.2

28
2.6
figure 02-06.jpg

• Figure 2.6

29
2.7
figure 02-07.jpg

• Figure 2.7

30
Table 2.2
table 02-02.jpg

• Table 2.2

31
Chemical Bonds Linking Atoms Together

• Nonpolar covalent bonds form when the
  electronegativities of two atoms are
  approximately equal. When atoms with strong
  electronegativity (such as oxygen) bond to atoms
  with weaker electronegativity (such as hydrogen),
  a polar covalent bond forms, in which one end is
  d and the other is d. Review Figure 2.8, Table
  2.3

32
2.8
figure 02-08.jpg

• Figure 2.8

33
Table 2.3
table 02-03.jpg

• Table 2.3

34
Chemical Bonds Linking Atoms Together

• Hydrogen bonds form between a d hydrogen atom in
  one molecule and a d nitrogen or oxygen atom in
  another molecule or in another part of a large
  molecule. Review Figure 2.9

35
2.9
figure 02-09.jpg

• Figure 2.9

36
Chemical Bonds Linking Atoms Together

• Ions, electrically charged bodies, form when an
  atom gains or loses one or more electrons. Ionic
  bonds are electrical attractions between
  oppositely charged ions. Review Figures 2.10,
  2.11

37
2.10
figure 02-10.jpg

• Figure 2.10

38
2.11
figure 02-11.jpg

• Figure 2.11

39
Chemical Bonds Linking Atoms Together

• Nonpolar molecules do not interact directly with
  polar substances. They are attracted to each
  other by very weak bonds called van der Waals
  forces. Review Figure 2.12

40
2.12
figure 02-12.jpg

• Figure 2.12

41
Chemical Reactions Atoms Change Partners

• In chemical reactions, substances change their
  atomic compositions and properties. Energy is
  either released or added. Matter and energy are
  not created or destroyed, but change form.

42
Chemical Reactions Atoms Change Partners

• Combustion reactions are oxidation-reduction
  reactions. Fuel is converted to carbon dioxide
  and water, while energy is released as heat and
  light. In living cells, these reactions occur in
  multiple steps. Review Figure 2.13

43
2.13
figure 02-13.jpg

• Figure 2.13

44
Water Structure and Properties

• Waters molecular structure and capacity to form
  hydrogen bonds give it unusual properties
  significant for life. Review Figure 2.15

45
2.15
figure 02-15.jpg

• Figure 2.15

46
Water Structure and Properties

• Cohesion of water molecules results in a high
  surface tension. Waters high heat of
  vaporization assures cooling when it evaporates.

47
Water Structure and Properties

• Solutions are substances dissolved in water.
  Concentration is the amount of a given substance
  in a given amount of solution. Most biological
  substances are dissolved at very low
  concentrations.

48
Acids, Bases, and the pH Scale

• Acids are substances that donate hydrogen ions.
  Bases are those that accept hydrogen ions.

49
Acids, Bases, and the pH Scale

• The pH of a solution is the negative logarithm of
  the hydrogen ion concentration. Values lower than
  pH 7 indicate an acidic solution. Values above pH
  7 indicate a basic solution. Review Figure 2.18

50
2.18
figure 02-18.jpg

• Figure 2.18

51
Acids, Bases, and the pH Scale

• Buffers are systems of weak acids and bases that
  limit the change in pH when hydrogen ions are
  added or removed. Review Figure 2.19

52
2.19
figure 02-19.jpg

• Figure 2.19

53
The Properties of Molecules

• Molecules vary in size, shape, reactivity,
  solubility, and other chemical properties.

54
The Properties of Molecules

• Functional groups make up part of a larger
  molecule and have particular chemical properties.

55
The Properties of Molecules

• The consistent chemical behavior of functional
  groups helps us understand the properties of the
  molecules that contain them. Review Figure 2.20

56
2.20 Part 1
figure 02-20a.jpg

• Figure 2.20 Part 1

57
2.20 Part 2
figure 02-20b.jpg

• Figure 2.20 Part 2

58
The Properties of Molecules

• Structural and optical isomers have the same
  kinds and numbers of atoms, but differ in their
  structures and properties. Review Figure 2.21

59
2.21
figure 02-21.jpg

• Figure 2.21

60
Osmosis and Diffusion
61
Condensation Reactions

• Longer polymer chains are formed and water is a
  product.
• OH and H are separated from smaller molecules to
  form larger polymers.
• Also called Dehydration Reactions.

62
Hydrolysis Reactions

• Water is separated to free a hydroxide group and
  a hydrogen ion to join to create smaller polymers.

63
Life The Science of Biology6th ed

• William K Purves, David Sadava, Gordon H Orians,
  H Craig Heller, Sinauer Associates, Inc., 2001