1. Chapter 4 “Atomic Theory and Structure”

2. OBJECTIVES: Explain Dalton’s atomic theory.
Identify the parts of an atom, their location, charge, and relative mass.
Determine the numbers of subatomic particles in an atom.

3. Democritus’s Atomic Philosophy
Democritus created the idea that all matter is made up of various imperishable, indivisible units, which he called atoma.
This idea was soon
rejected and forgotten.

4. Dalton’s Atomic Theory
All elements are composed of tiny indivisible particles called atoms.
2) Atoms of the same element are identical. Atoms of different elements are different.
John Dalton
(1766 – 1844)

5. Atoms of different elements combine in simple whole-number ratios to form chemical compounds
In chemical reactions, atoms are combined, separated, or rearranged, but never changed into atoms of another element.

6. What are the main components of the atom?
Atoms have two main regions
________________

7. One change to Dalton’s atomic theory is that atoms are divisible into subatomic particles:
Electrons
Protons
Neutrons

8. The Subatomic Particles
Location
Charge
Relative mass in amu
Function
Proton
Neutrons
Electrons

9. Atom Math Protons: atomic number Electrons: protons – charge
(same as protons if atom is neutral)
Neutrons: mass number – atomic number
protons: ________
electrons: ________
neutrons: ________

10. Atom Math Atomic number: Atomic mass: number of protons
(also electrons IF atom is neutral)
Atomic mass:
Average value of all isotopes
called mass number when rounded to nearest whole number
Mass Number equals protons + neutrons

11. Atomic Number Carbon Phosphorus Gold
Atomic number of an element is the number of protons in the nucleus of each atom of that element.
Element
Atomic Number
Number of Protons
Number of Electrons
Number of Neutrons
Carbon
Phosphorus
Gold

12. Ions When an atom loses or gains electrons it is called an ion
Loses—positive ion
Gains—negative ion

13. Ions-counting electrons
# electrons gain/lost
O -2
Al +3
Be +2
Br -1
K +1

14. Isotopes
Atoms of the same element can have different numbers of neutrons.
Thus, different mass numbers.

15. We can also put the mass number after the name of the element:
Naming Isotopes
We can also put the mass number after the name of the element:
carbon-12
carbon-14
uranium-235
uranium-238

16. Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons.
Protons
Electrons
Neutrons
Nucleus
Hydrogen–1 1
Hydrogen-2
(deuterium)
Hydrogen-3
(tritium) 2

17. Isotopes
Elements occur in nature as mixtures of isotopes.

18. Isotopes-counting neutrons
Mass # # Neutrons
Oxygen-18
Aluminum-25
10Be
79Br
Potassium-41

19. Relative Atomic Mass
Atoms are very small particles. It is very difficult to do calculations with the mass of an atom measured in grams.
Exmp. The mass of an atom of oxygen is g.
Instead, scientists use a relative unit of mass based on the mass of the nuclide Carbon-12 called the atomic mass unit.
Exmp. The mass of an oxygen atom is amu.

20. How are atomic number, atomic mass, and charge calculated?
Mass Number= Protons + ______________
Charge = Protons - _________________

21. Calculating Protons, Neutrons, and Electrons
Neutrons = Mass Number - ________
Electrons = Protons - __________

22. Complete Symbols
Contain the symbol of the element, the mass number and the atomic number.
Mass
number X
Superscript →
Atomic
number
Subscript →

23. Review Subatomic Particle Counting
How many protons, neutrons, and electrons are in Chromium?
P = atomic number = 24
N = mass # - protons = = 28
e = protons – charge = 24 – 0 = 24
How many protons, neutrons, and electrons are in the element with an atomic number of 57?
P = atomic number = 57
N = mass # - protons = = 82
e = protons – charge = 57 – 0 = 57

25. Chapter 4 Part 2“Isotopes”

29. Atomic Mass
The average atomic mass: is based on the abundance (percentage) of each variety of that element in nature.

30. To calculate the average atomic mass:
Multiply the atomic mass of each isotope by its abundance percentage (expressed as a decimal), then add the results.

31. Atomic Masses
Atomic mass is the average of all the naturally occurring isotopes of that element.
Isotope
Mass #
% in nature
Carbon-12
98.89%
Carbon-13
1.11%
Carbon-14
<0.01%
negligible
Carbon =

32. Average Atomic Mass
Rubidium has two common isotopes, Rb-85 and Rb-87. If the abundance of Rb-85 is 72.2% and the abundance of Rb-87 is 27.8%, what is the average atomic mass of rubidium?

33. On Your Own
Titanium has five common isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%), 49Ti (5.5%), 50 Ti (5.3%). What is the average atomic mass of titanium?

34. Poll everywhere response
Argon has three naturally occurring isotopes: argon-36, argon-38, and argon-40. Based on argon’s reported atomic mass, which isotope do you think is the most abundant in nature?

35. Calculate the weighted average atomic mass of the following mix of isotopes:
Total Number
Total Mass
Mass of one Atom
Percent Abundance
(in decimal form) A 15 45 B 5 10

36. Beanium: Atomic and Isotopic Mass

37. Purpose:
To illustrate the relationship between isotopic mass, isotopic abundance, and atomic mass.

38. Total # of atoms in sample Weighted average atomic mass for beanium
Data Table:
Total mass of sample
Total # of atoms in sample
Mass of one atom
Percent abundance
(in decimal form)
Isotopic mass
Weighted average atomic mass for beanium
Black
beanium
White
Spotted beanium
Total beanium sample 1

39. Related Questions: Show all work.
1. Chlorine: a. Chlorine exists in nature as chlorine-35 (% abundance = 75%) and chlorine-37 ( % abundance = 25%). Calculate the atomic mass of chlorine. b. What is the essential difference in the structure between the chlorine atoms found in question Number 1a? 2. Oxygen: Oxygen gas consists of isotopes with atomic masses of 16.00, 17.00, and amu. Their abundances are 99.76%, 0.04%, and 0.20% respectively. What is the atomic mass of oxygen? 3. Nitrogen: nitrogen has two isotopes, N-14 and N-15, with masses of amu and amu respectively. If the atomic mass of nitrogen is amu, what is the abundance of each isotope?

40. Total # of atoms in sample Weighted average atomic mass for beanium
Data Table:
Total mass of sample
Total # of atoms in sample
Mass of one atom
Percent abundance
(in decimal form)
Isotopic mass
Weighted average atomic mass for beanium
Black
beanium
White
Spotted beanium
Total beanium sample 1

41. Lab Report – Related Questions
Chlorine: Chlorine exists in nature as chlorine-35 (% abundance = 75%) and chlorine-37 (% abundance = 25%). Calculate the atomic mass of chlorine.
Oxygen: Oxygen gas consists of isotopes with atomic masses of 16.00, 17.00, and amu. Their abundances are 99.76%, 0.04%, and 0.20% respectively. What is the atomic mass of oxygen?
Nitrogen: nitrogen has two isotopes, N-14 and N-15, with masses of amu and amu respectively. If the atomic mass of nitrogen is amu, what is the abundance of each isotope?

42. Vocabulary Dalton Counting Ions Isotopes Weighted average atomic mass
What’s on the quiz?
Vocabulary
Dalton
Counting
Ions
Isotopes
Weighted average atomic mass

43. Dalton Counting Ions Isotopes Average atomic mass
Friday, September 20, 2013
BR: What is the structural difference between Chlorine-35 and Chlorine-37?
Dalton
Counting
Ions
Isotopes
Average atomic mass

44. Basic Atomic Theory Review

45. Basic Atomic Theory Review

46. Basic Atomic Theory Review

47. Basic Atomic Theory Review

48. Quiz Dalton Counting Ions Isotopes Average atomic mass
Friday, September 20, 2013
EQ: What characteristics of the atom are explained by the modern atomic theory?
Quiz
Dalton
Counting
Ions
Isotopes
Average atomic mass