Review

1
Review

• Scientist who discovered the electron using the
  cathode ray tube
• Thomson
• Scientist who used the oil drop experiment to
  discover the charge on the electron
• Millikan
• Scientist who conducted the gold foil experiment
  to discover that the nucleus is small, dense, and
  positively charged.
• Rutherford

2
Review

• Scientist that developed the pulsating planetary
  model
• Bohr
• Scientist that discovered the existence of the
  neutron
• Chadwick
• Scientist that had the solid sphere model of the
  atom
• Dalton

3
Review

• Greek philosopher who coined the term atom from
  the Greek word atomos
• Democritus
• Greek philosopher who did not believe in the atom
• Aristotle
• Scientist who created the law of definite
  proportions
• Proust

4
Review

• Scientist who created the law of multiple
  proportions
• Dalton
• Scientist who created the law of conservation of
  mass
• Lavoisier

5
Review
6

• An atom is the smallest particle of an element
  that gives it its chemical and physical
  properties.

• The atom is extremely small. One teaspoon of
  water has 3 times as many atoms as the Atlantic
  Ocean has teaspoons of water.

• If a large sports stadium were an atom, a marble
  would represent the nucleus.

7
Atom Structure

• An atom consists of a
• Positively charged nucleus that contains protons
  and neutrons
• Negatively charged electrons in space outside of
  the nucleus.

8
Atoms found in nature have a neutral charge. Why?
9
Atomic Number

• All atoms of the same element have the same
  number of protons in the nucleus

13
Al
26.981
10
Atomic Number

• Atomic protons
• electrons
• only for neutral atoms

11
Mass Number

• Mass Number
• protons neutrons
• NOT on the periodic table, electron is so small
  that its mass is negligible

12
Average Atomic Mass

• Weighted average, more abundant isotopes have a
  greater affect
• On the periodic table

13
Atomic Symbols

• Hyphen/mass notation - show the name of the
  element, a hyphen, and the mass number in
• sodium-23
• Nuclear symbol - show the mass number and atomic
  number next to the chemical symbol
• mass number
• 23 Na
• atomic number 11

14
Figure 3.10 Two isotopes of sodium.
15
Isotopes

• Atoms of the same element but different mass
  number.
• Boron-10 (10B) has 5 p and 5 n
• Boron-11 (11B) has 5 p and 6 n

16
Practice

• Ar-40
• P-31

17
Isotopes?

• Which of the following represent isotopes of the
  same element? Which element?
• 234 X 234 X 235 X 238 X
• 92 93 92 92

18

1. An __ ___ is the smallest particle of an
   element that has the chemical properties of the
   element.

2. The 3 particles that make up the atom are
________, _________, and _________.
3. Atoms with the same number of protons and
electrons, but a different number of neutrons are
called ____________.
4. ___________ was an English scientist who
developed an atomic theory in the early 1800s.