1. Ch. 3 - Atomic Structure

2. Foundations of Atomic Theory
Chapter 3
Foundations of Atomic Theory
Law of conservation of mass: mass is neither created nor destroyed during ordinary chemical reactions or physical changes

3. Foundations of Atomic Theory, continued
Chapter 3
Foundations of Atomic Theory, continued
Law of multiple proportions: if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers

4. Foundations of Atomic Theory, continued
Law of definite proportions: a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound

5. Law of Definite Proportions
Chapter 3
Law of Definite Proportions
Click below to watch the Visual Concept.
Visual Concept

6. Dalton’s Atomic Theory
Chapter 3
Dalton’s Atomic Theory
All matter is composed of extremely small particles called atoms.
Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
Atoms cannot be subdivided, created, or destroyed. can’t be broken down (Conservation of mass)
Atoms of different elements combine in simple whole- number ratios to form chemical compounds. (multiple proportions)
In chemical reactions, atoms are combined, separated, or rearranged.

7. Modern Atomic Theory Chapter 3
Some important concepts remain unchanged.
All matter is composed of atoms.
Atoms of any one element differ in properties from atoms of another element.
Not all aspects of Dalton’s atomic theory have proven to be correct. We now know that:
Atoms are divisible into even smaller particles.
A given element can have atoms with different masses.

8. History of the Atomic Structure
Day 2- Chapter 3
History of the Atomic Structure

9. History of the Atom
Atomic models are constructed to explain experimental evidence and make predictions
Changes in the atomic model over time exemplify how scientific knowledge changes as new evidence emerges and technological advancements like electricity extend the boundaries of scientific knowledge

10. Discovery of the Electron
Cathode Rays and Electrons
Experiments in the late 1800s by Thompson, showed that cathode rays were composed of negatively charged particles.
These particles were named electrons
Also developed the plum pudding model of the atom

11. Discovery of the Electron, continued…..
Particles pass through tube from cathode (-) to the anode (+)
1. Cathode rays were deflected by a magnetic field
2. Rays were deflected away from a negatively charged object
These observations led to hypothesis that the particles that compose cathode rays are negatively charged

12. Thomson’s Cathode-Ray Tube Experiment
Chapter 3
Thomson’s Cathode-Ray Tube Experiment
Click below to watch the Visual Concept.
Visual Concept

13. Discovery of the Atomic Nucleus
More detail of the atom’s structure was provided in 1911 by Ernest Rutherford
The results of their gold foil experiment led to the discovery of a very densely packed bundle of matter with a positive electric charge.
Rutherford called this positive bundle of matter the nucleus.

14. Discovery of the Atomic Nucleus Cont….

15. Rutherford’s Gold Foil Experiment
Chapter 3
Rutherford’s Gold Foil Experiment
Click below to watch the Visual Concept.
Visual Concept

16. The Structure of the Atom
Chapter 3
The Structure of the Atom
An atom is the smallest particle of an element that retains the chemical properties of that element.
The nucleus is a very small region located at the center of an atom.
The nucleus is made up of at least one positively charged particle called a proton and usually one or more neutral particles called neutrons. (except for some Hydrogen)
The nuclei of atoms of different elements differ in their number of protons
number of protons determines that atom’s identity.

17. The Structure of the Atom, continued
Chapter 3
The Structure of the Atom, continued
Surrounding the nucleus is a region occupied by rapidly moving negatively charged particles called electrons
Protons, neutrons, and electrons are often referred to as subatomic particles.
Most of the atom is EMPTY space

18. The Structure of the Atom, cont……
A proton has a positive charge equal in magnitude to the negative charge of an electron.
Atoms are electrically neutral because they contain equal numbers of protons and electrons.

19. Properties of Subatomic Particles
Chapter 3
Properties of Subatomic Particles

20. Forces in the Nucleus
When two protons are extremely close to each other, there is a strong attraction between them
A similar attraction exists when neutrons are very close to each other or when protons and neutrons are very close together
short-range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together are referred to as nuclear forces.

21. Chapter 3 https://www.youtube.com/watch?v=FSyAehMdpyI
Click below to watch the Visual Concept.
Visual Concept

22. Day 3- Chapter 3
Atomic Structure

23. Review ???? Review ???? What is the charge of a neutron?
A molecule of carbon monoxide, CO, has one atom of oxygen while a molecule of carbon dioxide, CO2, has two. In a sample of CO containing 1 g of carbon, 1.33 g of oxygen will combine with the carbon to form the molecule. What is the mass of oxygen in a sample of CO2 containing 1 g of carbon?
a.1.33 g b.3.0 g c.2.66 g d.0.0 g
What is the charge of a neutron?
Most of an atom is ___________
Where are electrons found?
What is the nucleus of an atom made up of?

24. Chapter 3
Atomic Number
Atoms of different elements have different numbers of protons.
Atoms of the same element all have the same number of protons.
The atomic number of an element is the number of protons of each atom of that element.

25. Mass Number always a whole number NOT on the Periodic Table!
mass # = protons + neutrons
always a whole number
NOT on the Periodic Table!
Publishing Company, Inc.

26. Isotopes Mass # Atomic # Nuclear symbol: Hyphen notation: carbon-12
Atoms of the same element with different mass numbers. B/C they differ in # of neutrons
Nuclear symbol:
Mass #
Atomic #
Hyphen notation: carbon-12

27. Isotopes
© Addison-Wesley Publishing Company, Inc.
C. Johannesson

28. Isotopes Chlorine-37 atomic #: 17 mass #: 37 # of protons:
# of electrons:
# of neutrons: 17 37 20

29. Average Atomic Mass Avg. Atomic Mass weighted average of all isotopes
on the Periodic Table
round to 2 decimal places
Avg.
Atomic
Mass

30. Average Atomic Mass Avg. Atomic 16.00 Mass amu
EX: Calculate the avg. atomic mass of oxygen if its abundance in nature is 99.76% 16O, 0.04% 17O, and 0.20% 18O.
Avg.
Atomic
Mass
16.00
amu

31. Ch 3- The mole
Counting atoms

32. Day 3 Review ???? Review ???? An atom is electrically neutral because?
Isotopes are atoms of the same element that have different?
Most of the volume of an atom is occupied by the _______
All atoms of the same element have the same ____________

33. What is the Mole?
A counting number (like a dozen) describes the number of particles
Avogadro’s number (NA)
1 mol = 6.02  1023 items
Because mass of an atom is very small, the mole is used to translate between the atomic and macroscopic levles
The mole is equal to the number of particles in exactly 12 grams of carbon-12 atoms.

34. HOW LARGE IS IT???
1 mole of hockey pucks would equal the mass of the moon!
1 mole of basketballs would fill a bag the size of the earth!
1 mole of pennies would cover the Earth 1/4 mile deep!

35. Molar Mass Mass of 1 mole of an element or compound. - Molar mass
Equal to Average atomic mass units per atom (amu) found on periodic table also equal to the formula mass if it is a compound
Written in units grams per mole (g/mol)

36. Molar Mass Examples carbon aluminum zinc 12.01 g/mol 26.98 g/mol

37. Formula Mass Examples water H2O sodium chloride
2(1.01) = g/mol
NaCl
= g/mol

38. formula Mass Examples sodium bicarbonate NaHCO3 sucrose
(16.00) = g/mol
C12H22O11
12(12.01) + 22(1.01) + 11(16.00) = g/mol

39. The Mole Chapter 3 https://www.youtube.com/watch?v=o7JeKIS9RSQ
Click below to watch the Visual Concept.
Visual Concept

40. Chapter 3 Day 5

41. Molar Conversions molar mass 6.02  1023 MOLES MASS IN GRAMS NUMBER OF
(Periodic Table)
6.02  1023
MASS IN
GRAMS
MOLES
NUMBER OF
Atoms/molecule

42. Chapter 3
Solving Mole Problems

43. Relating Mass to Numbers of Atoms, continued
Chater 3
Relating Mass to Numbers of Atoms, continued
Given: 11.9 g Al
Unknown: amount of Al in moles
Solution:
The molar mass of aluminum from the periodic table is rounded to g/mol.

44. Molar Conversion Examples
How many moles of carbon are in 26 g of carbon?
26 g C
1 mol C
12.01 g C
= 2.2 mol C

45. Molar Conversion Examples
How many grams of carbon are in 4.0 moles of carbon?
4.0 mol C
12.01 g C
1 mol C
= 48 g C

46. Relating Mass to Numbers of Atoms, continued
Chapter 3
Relating Mass to Numbers of Atoms, continued
Given: 3.01 × 1023 atoms of Ag
Unknown: amount of Ag in moles
Solution:

47. Molar Conversion Examples
How many molecules are in 2.50 moles of C12H22O11?
6.02  1023
molecules
1 mol
2.50 mol
= 1.51  1024
molecules
C12H22O11

48. Molar Conversion Examples
Find the mass of 2.1  1024 molecules of NaHCO3.
2.1  1024
molecules
1 mol
6.02  1023
molecules
84.01 g
1 mol
= 290 g NaHCO3