1. The Structure of the Atom

2. Important contributors to the Atomic Theory
Democritus Dalton Rutherford
Aristotle J. J. Thomson Bohr

3. The Atom: Early Theories
Democritus versus Dalton similarities
Both believed
Matter composed of extremely small particles called atoms
All atoms of a given element are identical, but different from the atoms of other elements
Atoms could not be created, divided, or destroyed
Apparent changes in matter result from changes in the groupings of atoms

4. The Atomic Theory: Democritus and Dalton differences
Matter is composed of empty space through which atoms move
Different kinds of atoms come in different sizes and shapes
The differing properties of atoms are due to the size, shape, and movement of atoms
Dalton
Different atoms combine in simple whole number ratios to form compounds

5. Dalton’s Atomic Theory

6. The Atom: Subatomic particles and the nuclear atom
How were the various parts of the atom discovered?
Electrons were discovered by the experiments of many scientists using cathode rays.
JJ Thomson was able to determine the ratio of the electron’s charge to its mass
Robert Millikan determined the charge of the electron and was able to calculate the mass of a single electron

7. J. J. Thomson: Plum Pudding Model

8. Discovery of subatomic particles
The nucleus was discovered by Ernest Rutherford and his gold foil experiment
Rutherford refined his definition to include the proton
Rutherford and James Chadwick discovered the neutron

9. The atom Bohr- e- only have “allowable E states”
e- around nucleus in orbits
Particle
Symbol
Location
Relative charge
Relative mass
Actual mass (g)
electron e-
electron cloud 1-
1/1840
9.11 x 10-28
proton p+
nucleus 1+ 1
1.673 x 10-24
neutron n0
1.675 x 10-24

10. The Atom: How Atoms Differ
Hydrogen 1 H
Chemical name
Atomic number
Chemical Symbol
Average Atomic Mass
Atomic number = number of protons = number of electrons
How many protons and electrons are in each of the following atoms?
boron
radon
platinum
magnesium
An atom of an element contains 66 electrons. What element is it?
An atom contains 14 protons. What element is it?

11. LET’S REVIEW… Which scientist came up with the plum pudding model?
Why was it called this?
Who discovered the nucleus of the atom?
What was wrong with Dalton’s atomic theory?
How many protons, neutrons, and electrons are in each of the following atoms?
boron
radon

12. Let’s Review: Answers
Which scientist came up with the plum pudding model? J. J. Thomson
Why was it called this?
Who discovered the nucleus of the atom?
Rutherford
What was wrong with Dalton’s atomic theory?
He stated that the atom was “indivisible”
How many protons, neutrons, and electrons are in each of the following atoms?
Boron: p+, e- = 5, no= 6
Radon: p+, e- = 86, no= 136

13. The Atom: How Atoms Differ cont
Isotopes
An element with a different amount of neutrons in its nucleus
PROTON determines the ID
Representing isotopes:

14. How atoms differ Element – mass #
carbon – 12, carbon – 13, carbon – 14
The mass number represents the total protons and neutrons in an element
How many protons, electrons, and neutrons in the following isotopes? Name each isotope and write its symbol.

15. Atomic Structure: Isotopes
Atomic masses of elements on the table are based on naturally occurring isotopes
Weighted scale – abundance(mass)
Average atomic mass =
(mass 1 x rel. abundance 1) + (mass 2 x rel. abundance 2)
Element C has two naturally occurring isotopes. The isotope with mass number 10 has a relative abundance of 20%. The isotope with mass number 11 has a relative abundance of 80%.
Use these figures to estimate the average atomic mass for element C. State the atomic number and the true value of element C

16. Atomic Structure: Isotopes
Complete the following table
Isotope
Atomic #
Mass # p+ e- n0
symbol 20 46 8 17 Ag
hydrogen-3
107 47

17. Types of Radiation
Alpha Radiation: radiation that is deflected toward the negatively charged plate. Each alpha particle contains two protons and two neutrons.
Beta Radiation: radiation that was deflected toward the positively charged plate. Each beta particle is an electron.
Gamma Radiation: high energy radiation that possesses no mass

18. The Atom Review Atomic theories Democritus vs. Dalton
Subatomic particles and the atom
JJ Thompson – determined the charge to mass ratio of the electron
Robert Millikan – determined the charge and mass of the electron
Rutherford – discovered the nucleus and later the proton
Rutherford and James Chadwick – discovered the neutron
Atomic Number
Isotopes
Average Atomic Mass
Types of Radiation