Title: Atoms
1Atoms
- Smallest electrically neutral particle of an
element that retains the properties of that
element.
2Democritus
- 4th century B.C. in Greece
- Indestructible indivisible tiny particles
called atoms
3John Dalton
- (1766-1844) English
- Experimental evidence
- Ratios in which elements combine in chemical
reactions
4Daltons atomic theory
- All elements are composed of tiny indivisible
particles called atoms.
5Daltons atomic theory
- Atoms of the same element are identical. The
atoms of any 1 element are different from those
of any other element.
6Daltons 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.
7Daltons 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.
8Error in Daltons Atomic Theory
- atoms are divisible
- now can identify subatomic particles
9Just How Small is an Atom
- copper atoms lined up 1 cm long 107 100 000
000. Cu atoms - Approximately the width of a penny.
10Atomic Structure
- Atoms composed of e-, p, no
- Nucleus is p no
11Electrons
- Negatively charged subatomic particles
- J.J. Thompson discovered in 1897
12Protons
- Protons in atoms are equal to of electrons
- Have 1 charge
- Mass 1840x an electron
13Neutrons
- Have no charge
- Same relative mass as proton
14Atomic 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-
15Periodic Table
16Mass 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
17Isotopes
- Atoms w/ same of p but different of no
- Also has different mass
18Isotopes
- Despite this difference they are chemically alike
- Same of p e-
- P e- are responsible for chemical behavior
19H and C Isotopes
20Atomic 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
21Periodic Table
22Atoms The Constituents of Matter
- Electrons are distributed in shells of orbitals
containing a maximum of two. Review Figures 2.4,
2.5
232.4
figure 02-04.jpg
242.5
figure 02-05.jpg
25Atoms The Constituents of Matter
- An atom can combine with other atoms to form
molecules. Review Table 2.1
262.1
27Chemical 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
282.6
figure 02-06.jpg
292.7
figure 02-07.jpg
30Table 2.2
table 02-02.jpg
31Chemical 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
322.8
figure 02-08.jpg
33Table 2.3
table 02-03.jpg
34Chemical 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
352.9
figure 02-09.jpg
36Chemical 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
372.10
figure 02-10.jpg
382.11
figure 02-11.jpg
39Chemical 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
402.12
figure 02-12.jpg
41Chemical 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.
42Chemical 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
432.13
figure 02-13.jpg
44Water Structure and Properties
- Waters molecular structure and capacity to form
hydrogen bonds give it unusual properties
significant for life. Review Figure 2.15
452.15
figure 02-15.jpg
46Water Structure and Properties
- Cohesion of water molecules results in a high
surface tension. Waters high heat of
vaporization assures cooling when it evaporates.
47Water 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.
48Acids, Bases, and the pH Scale
- Acids are substances that donate hydrogen ions.
Bases are those that accept hydrogen ions.
49Acids, 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
502.18
figure 02-18.jpg
51Acids, 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
522.19
figure 02-19.jpg
53The Properties of Molecules
- Molecules vary in size, shape, reactivity,
solubility, and other chemical properties.
54The Properties of Molecules
- Functional groups make up part of a larger
molecule and have particular chemical properties.
55The 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
562.20 Part 1
figure 02-20a.jpg
572.20 Part 2
figure 02-20b.jpg
58The 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
592.21
figure 02-21.jpg
60Osmosis and Diffusion
61Condensation 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.
62Hydrolysis Reactions
- Water is separated to free a hydroxide group and
a hydrogen ion to join to create smaller polymers.
63Life The Science of Biology6th ed
- William K Purves, David Sadava, Gordon H Orians,
H Craig Heller, Sinauer Associates, Inc., 2001