Download Chapter 4 4.1 Defining the Atom • Early Models of the Atom atom

October 14, 2016
Chapter 4
4.1 Defining the Atom
• Early Models of the Atom
atom - smallest particles of an element that retains it's
identity in a chemical reaction
• Democritu's Atomic Philosophy (460 BC - 370 BC)
- Atoms are:
- Indivisible
- Indestructible
- He didn't:
- Explain chemical behavior
- have experimental support
• Dalton's Atomic Theory(1766-1844)
1) All elements are composed of tiny indivisible particles
called atoms
2) Atoms of the same element are identical. Atoms of any
one element are different from those of any other
element
3) Atoms of different elements can physically mix together
or can chemically combine in simple whole-number
ratios to form compounds.
4) Chemical reactions occur when atoms are separated
from each other, joined, or rearranged in a different
combination. Atoms of one element, however, are never
changed into atoms of another element as a result of a
chemical reaction.
October 14, 2016
Sizing up the Atom
• Pure copper coin the size of a penny contains about
2 x 1022
- earth's population is about 7 x 109 people
• Can see individual atoms with a scanning e- microscope
A scanning electron microscope was used to produce
this color-enhanced image of nickel atoms
October 14, 2016
4.2 Structure of the Nuclear Atom
• Subatomic particles
- 3 types:
electrons eprotons p+
neutrons n0
• J.J. Thomson (1856-1940)
- Discovered e- using a cathode ray tube
Robert A. Millikan (1869-1953)
experimentally determined the charge and mass of an
electron with his oil drop experiment
• Eugen Goldstein (1850-1930) discovered protons using
a cathode ray tube in 1886
• James Chadwick (1891-1974) discovered the neutron
in 1932
• Theoretical physicists believe that protons and neutrons
are made up of quarks
October 14, 2016
The Atomic Nucleus
J.J. Thomson had the plum-pudding model (blueberry
muffin)
Rutherford's gold-foil experiment (1911) - discovered the
nucleus of the atom.
October 14, 2016
Homework:
P 104 # 6-8
P 109 # 11,13,14,15
P 122 # 40-43, 45,46