1. Chapter 4
Atomic Structure

2. Defining the Atom Early Models of the Atom
Democritus – Greek philosopher suggested the existence of the atom around 400 BC
Atoms are _____________________
Idea lacked ______________ support
Idea challenged by ________________

3. Dalton – early 1800’s (2000 yrs. after Democritus)
Used experiments (Scientific Method)
Studied the nature of atoms & ratios in which elements combine in chemical reactions
Dalton’s Atomic Theory: page 102

4. 1 - All elements are composed of _____________________________________
4.1
1 - All elements are composed of _____________________________________
According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?

5. 4.1
2 - Atoms of the same element are _________. The atoms of any one element are ___________ from those of any other element.
According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?

6. 4.1
3 - Atoms of different elements can _________mix together or can _______________________________________.
According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?

7. 4.1
4 - Chemical reactions occur when atoms are _________________________. Atoms of one element are _____________________________________in a chemical reaction.
According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?
Scientists used a scanning tunneling microscope to generate this image of iron atoms, shown in blue. The radius of this circle of atoms is just 7.13 × 10-9 m.

8. Atoms are defined today as _____________________________________
Atoms today are observable with scanning tunneling microscope
Dalton’s work stimulated much scientific research into the structure of the atom

9. Page 103, Section assessment # 1 to 7, skip 6
READ pages 104, 105 summarize JJ Thomson’s use of cathode ray tube

10. Structure of the Nuclear Atom
Subatomic Particles
Electrons
JJ Thomson used cathode ray tube to discover ___________, 1897
Figures 4.4, 4.5
Concluded that electrons must be parts of atoms of all elements
Millikan – electron ___________________

11. Protons
E Goldstein used cathode ray tube and found rays traveling in opposite direction to cathode ray, 1886
Concluded that rays were made of ____________________
Protons have mass __________________

12. Table 4.1 – Properties of Subatomic Particles
Neutrons
_______________ confirmed the existence of neutrons, 1932
Particle with ____ charge, mass equal to ___________
Table 4.1 – Properties of Subatomic Particles

13. 4.2
Subatomic Particles
Table 4.1 summarizes the properties of electrons, protons, and neutrons.

14. The Atomic Nucleus
Scientists tried to answer the question, How are subatomic particles put together in the atom?
JJ Thomson – the ‘plum pudding’ model:

15. The Atomic Nucleus Rutherford’s Gold-Foil Experiment 4.2
In 1911, Rutherford and his coworkers at the University of Manchester, England, directed a narrow beam of alpha particles at a very thin sheet of gold foil.

16. E Rutherford – student of Thomson
Gold foil experiment – figure 4.7
In the plum pudding model, alpha particles should pass through the foil with slight deflections caused by the positive charge spread throughout the gold atoms
Results showed that ____________________________________

17. Rutherford’s new theory:
atom is mostly _______________
Positive charge is concentrated in small region – ____________
Nuclear atom – small nucleus with protons and neutrons; electrons occupy most of the volume

18. Page 108, Section Assessment, # 8 -14
Page 110, Vocabulary

19. Distinguishing Among Atoms
Atomic Number
# of _____________
Identifies an atom
All atoms are neutral, therefore, ______________________________
Table 4.2
Page 111, Practice Problems #15, 16

20. 4.3
Atomic Number

21. Page 112, Sample Problem 4.1, Practice Problems # 17 & 18
Mass Number
Total # of ________ + _____________
# neutrons = ______ # - _________ #
Atomic notation
2 forms, page 111, last sentence
Page 112, Sample Problem 4.1, Practice Problems # 17 & 18

22. Mass Number 4.3 Au is the chemical symbol for gold.
Au is the chemical symbol for gold. Applying Concepts How many electrons does a gold atom have?

23. for Sample Problem 4.1

24. Page 113, Conceptual Problem 4.2, Practice Problems # 19 & 20
Isotopes
Same #______ but different # ________, therefore, different ________ #
Figure 4.9
Isotopes of Hydrogen: page 113
Page 113, Conceptual Problem 4.2, Practice Problems # 19 & 20

25. Atomic Mass
Amu – atomic mass unit, unit that measures mass of atoms and subatomic particles
1 amu = 1/12 mass of carbon-12 ( mass of carbon-12 is assigned to be 12 amu
Proton mass = neutron mass = 1 amu = 1.67 x grams

26. Electron mass = 9.11 x 10-28 grams
Most elements occur as a mixture of 2 or more isotopes
Atomic mass is a weighted average atomic mass that reflects both the mass and ___________________ of each isotope
Table 4.3

27. Page 115, Sample Problem Calculate average atomic mass:
Mass of each isotope x % abundance
Add products
Page 115, Sample Problem

28. Periodic Table
Arrangement of elements based on _________________________
Arranged in order of increasing atomic ______________
Period – horizontal row – properties vary as you move across the period, and repeat in each row
Group – vertical column – elements in groups have similar chemical and physical properties

29. Page 119, Section Assessment, # 25 – 33 Chapter 4 Assessment
Page , #34-73, skip 38,62,67,68
Page 124, #74, 79, 80
Standardized Test Prep page 125, # 1 - 9